Abstract: STL files are widely used in many needing 3D models fields. The main problem of STL files is their various errors. In order to repair them, the errors are classified by their characteristics first. Then the check of sides is employed as the base for STL files errors check, and the checked errors are recorded in arrays of error facets, sides and points, using an errors descriptive graph to represent the topology of checked error elements. In taking account of the characteristics of different errors, we propose a basic repair process, step-by-step ordered by points unitization→holes repair→cracks repair→redundance deletion→overlap repair→errors refresh. Finally, a corresponding repair tool is developed, and verified by an example.