This paper presents a study on effect of two mechanical impact parameters on impact mode piezoelectric power generation. The parameters are velocity and mass. Free fall experiment is used as the evaluation method. It turns out that peak of instantaneous output voltage is proportional to the impact velocity and for output power it is in a straight line relationship with the same parameter. For the same impact velocity, advantage in the usage of heavy object becomes clearer as its momentum and impact force are higher. However, adjustment in the velocity of impact is found to be more effective for higher instantaneous output power than the mass. This is proven by the output power which has been generated by 4g steel ball with momentum of 4.34gm/s is nearly 300% higher than that of 8g steel ball for the same momentum. Further analysis with forced vibration-based impact mode piezoelectric power generation experiment shows that the same conclusion can be made.