Bitron, as a new type of high-power microwave device, is studied in this paper. The parameters (such as microwave power and its efficiency) based on the theoretical analysis has been realized on 25D Particle in Cell (PIC) simulation code. This device is composed of two parts: a modulation cavity and an output cavity . Coupling exists between these two cavities, so the oscillation occurs under ce rtain conditions. X band bitron is designed in this paper, and its theoretical e fficiency is 294%. The process is also realized by 25 PIC simulation code, w ith an efficiency 28%, microwave frequency 942GHz, and the power output 2 25GW.