I build a homology model used by Swiss-model, and evaluate the model by SAVEs, but how to further optimizing the model? what tools can I use?
Please read this post on how to ask a good scientific question, and then consider to rephrase your question, providing more details in order to motivate people to answer.
Do energy minimization to refine the model by relaxing the steric clashes. You can use spdbv viewer to do that.
There are several tools that you could refine your 3D model e.g. TIGRESS, PREFMD that use different methodological approaches to refine the protein structure models.