Abstract: A cyclotron was designed using the 2.5 dimensional particle simulation code KARAT in the paper. Transverse momentum of the electrons was imparted by a kicker. By using intense coupling and optimized length of the interaction space, the device could generate microwave pulse with a peak power of 7 MW, an operating frequency of 38.5 GHz with the diving electron beam of 250 kV, 200 A and 1 ns. The peak power conversion reached 14%. The peak power had a square relationship with the beam pulse width during certain range, which was in accordance with the character of superradiance.