Parameter-efficient fine-tuning methods adjust a small subset of parameters in large models, achieving performance comparable to or even surpassing that of models fine-tuned with the full parameter set, and significantly reducing the time and computational costs associated with the fine-tuning process. Despite the developments of parameter-efficient fine-tuning methods for large models, we observe significant performance disparities across different vision tasks. We attribute this pronounced performance variability to the insufficient robustness of current parameter-efficient fine-tuning methods. In this paper, we propose a robust reparameterization framework for parameter-efficient fine-tuning. This framework has a dynamic training structure and introduces no additional computational overhead during the inference stage. Specifically, we propose Dropout-Mixture Low-Rank Adaptation (DMLoRA), which incorporates multiple up and down branches, to provide the model with a more robust gradient descent path. As training proceeds, DMLoRA gradually drops out branches to achieve a balance between accuracy and regularization. Additionally, we employ a 2-Stage Learning Scalar (LS) strategy to optimize the scale factor for each layer's DMLoRA module. Experimental results demonstrate that our method achieves state-of-the-art performance on the benchmark VTAB-1k and FGVC datasets for parameter-efficient fine-tuning.