Surface roughness is the most important standard to measure the polishing effect.The mathematic model of surface roughness with polishing time in electrolysis and plasma polishing is established on the basis of the polishing mechanism in this paper.The roughness of the specimen with different polishing time was measured.Nonlinear fitting of the experimental data and the mathematic model is carried out,by which the mathematic model is improved.It is reasonable and feasible to use the improved mathematic mode...