Objective To analyze the microparticles (MPs) morphology and pixel distribution of TiN coatings under different negative bias voltage (0, 100, 200, 300 and 400V), so as to provide basic data for industrial applications of multi-arc ion plating. Methods TiN coatings were deposited on hard alloy surface by multi-arc ion plating at different bias voltage. The surface morphology of TiN coatings was characterized by scanning electron microscope (SEM). At the same time, the amount and size of MPs were analyzed and the distribution of pixel was counted by ImageJ software. Results The amount of MPs on coating surface increased at first and then decreased with the increase of bias voltage. The maximum value was 1364 at 100 V and the minimum was 750 at 300 V. In addition, the area ratio of MPs on coating surface decreased gradually with the increase of bias voltage. The maximum value with worst mechanical properties was 6. 9% at 0 V and the minimum with best mechanical properties was 3. 3% at 400 V. The amount of light and dark pixel reached a maximum of 8302 at 300 V and a minimum of 4067 at 400 V. Conclusion The TiN coatings with best mechanical properties, low amount and small size of MPs were deposited at 400 V for 1 h with 30% duty cycle.