Abstract: To explore a new way for ultra-precision machining of soft metal balls,ultra precision mirror polishing Technology was adopted for mirror processing experiments of soft metal balls. The experiments show that polishing pressure,polishing liquid pH,particle size,and polishing pad thickness are the main factors to affect the surface quality. When the polishing pressure is ranged from 0. 6 to 0. 8 N / cm²,polishing liquid pH value of 10,abrasive particle size for W0. 5,and polishing pad thickness of 2 mm,the polishing effect can be optimal. It can effectively improve the machining efficiency,improve the quality of surface processing,and get the surface roughness Ra 0. 039 μm of machined surface.