Phosphor coating is one of the key steps in high-power LED packaging processes, among which the design of phosphor droplet ejecting head is the pivotal technology. Through the simplification of force displacement equation of piezoelectric actuator, the force-displacement equation of piezoelectric actuator is obtained. When considering the fluid movement, to avoid the complex analysis of the fluid movement in the cavity, the law of mass and energy conservation is employed, which will greatly simplify the analyzing procedure. As a result, the mathematical model of piezoelectric actuated micro-droplet jetting process is built. The calculating results and jetting rules shown by the model are basically according with the practically measured values.