diff --git a/src/llmtuner/chat/vllm_engine.py b/src/llmtuner/chat/vllm_engine.py
index 67a19b68..786e743d 100644
--- a/src/llmtuner/chat/vllm_engine.py
+++ b/src/llmtuner/chat/vllm_engine.py
@@ -10,6 +10,7 @@ from .base_engine import BaseEngine, Response
 
 if is_vllm_available():
     from vllm import AsyncEngineArgs, AsyncLLMEngine, RequestOutput, SamplingParams
+    from vllm.lora.request import LoRARequest
 
 if TYPE_CHECKING:
     from ..hparams import DataArguments, FinetuningArguments, GeneratingArguments, ModelArguments
@@ -24,7 +25,8 @@ class VllmEngine(BaseEngine):
         generating_args: "GeneratingArguments",
     ) -> None:
         config = load_config(model_args)  # may download model from ms hub
-        load_dtype = infer_optim_dtype(model_dtype=getattr(config, "torch_dtype", None))
+        infer_dtype = infer_optim_dtype(model_dtype=getattr(config, "torch_dtype", None))
+        infer_dtype = str(infer_dtype).split(".")[-1]
 
         self.can_generate = finetuning_args.stage == "sft"
         self.tokenizer = load_tokenizer(model_args)
@@ -36,15 +38,20 @@ class VllmEngine(BaseEngine):
             model=model_args.model_name_or_path,
             trust_remote_code=True,
             download_dir=model_args.cache_dir,
-            dtype=str(load_dtype).split(".")[-1],
+            dtype=infer_dtype,
             max_model_len=model_args.vllm_maxlen,
             tensor_parallel_size=get_device_count() or 1,
             gpu_memory_utilization=model_args.vllm_gpu_util,
             disable_log_stats=True,
             disable_log_requests=True,
             enforce_eager=model_args.vllm_enforce_eager,
+            enable_lora=model_args.adapter_name_or_path is not None,
         )
         self.model = AsyncLLMEngine.from_engine_args(engine_args)
+        if model_args.adapter_name_or_path is not None:
+            self.lora_request = LoRARequest("default", 1, model_args.adapter_name_or_path[0])
+        else:
+            self.lora_request = None
 
     async def _generate(
         self,
@@ -98,7 +105,11 @@ class VllmEngine(BaseEngine):
             skip_special_tokens=True,
         )
         result_generator = self.model.generate(
-            prompt=None, sampling_params=sampling_params, request_id=request_id, prompt_token_ids=prompt_ids
+            prompt=None,
+            sampling_params=sampling_params,
+            request_id=request_id,
+            prompt_token_ids=prompt_ids,
+            lora_request=self.lora_request,
         )
         return result_generator
 
diff --git a/src/llmtuner/hparams/parser.py b/src/llmtuner/hparams/parser.py
index a7d0a17f..c922dc47 100644
--- a/src/llmtuner/hparams/parser.py
+++ b/src/llmtuner/hparams/parser.py
@@ -308,15 +308,15 @@ def get_infer_args(args: Optional[Dict[str, Any]] = None) -> _INFER_CLS:
         if finetuning_args.stage != "sft":
             raise ValueError("vLLM engine only supports auto-regressive models.")
 
-        if model_args.adapter_name_or_path is not None:
-            raise ValueError("vLLM engine does not support LoRA adapters. Merge them first.")
-
         if model_args.quantization_bit is not None:
-            raise ValueError("vLLM engine does not support quantization.")
+            raise ValueError("vLLM engine does not support bnb quantization (GPTQ and AWQ are supported).")
 
         if model_args.rope_scaling is not None:
             raise ValueError("vLLM engine does not support RoPE scaling.")
 
+        if model_args.adapter_name_or_path is not None and len(model_args.adapter_name_or_path) != 1:
+            raise ValueError("vLLM only accepts a single adapter. Merge them first.")
+
     _verify_model_args(model_args, finetuning_args)
     _check_extra_dependencies(model_args, finetuning_args)
 
diff --git a/src/llmtuner/webui/chatter.py b/src/llmtuner/webui/chatter.py
index ee28603e..82e7b7f1 100644
--- a/src/llmtuner/webui/chatter.py
+++ b/src/llmtuner/webui/chatter.py
@@ -31,7 +31,10 @@ class WebChatModel(ChatModel):
         if demo_mode and os.environ.get("DEMO_MODEL") and os.environ.get("DEMO_TEMPLATE"):  # load demo model
             model_name_or_path = os.environ.get("DEMO_MODEL")
             template = os.environ.get("DEMO_TEMPLATE")
-            super().__init__(dict(model_name_or_path=model_name_or_path, template=template))
+            infer_backend = os.environ.get("DEMO_BACKEND", "huggingface")
+            super().__init__(
+                dict(model_name_or_path=model_name_or_path, template=template, infer_backend=infer_backend)
+            )
 
     @property
     def loaded(self) -> bool: