NiP basic substrates of hard disks were polished by electrochemical-mechanical polishing (ECMP) method with home-made slurry and a modified polisher. The effects of voltage, table rotation speed, pressure and slurry flow rate on the removal rate were investigated. The electrochemical mechanical polishing mechanism was primarily analyzed. The results show that NiP substrate can be polished with ECMP method at low pressure (3.5 kPa) and the material removal rate (MRR) can be controlled by adjusting polishing voltage, rotation speed of polishing table and slurry flow rate.