Based on the GaAs planar Schottky diode process， a W band wideband frequency tripler MMIC is designed with a reverse parallel diode pair. By combining the finite element method and equivalent circuit method， an accurate equivalent circuit model of the planar Schottky diode is built in the frequency range of 10~280 GHz. The nonlinear harmonic balance tool is utilized to achieve the optimal frequency tripler design in the W band. The measurement results show that the frequency multiplication loss is less than 15 dB under 17 dBm driving power， and efficiency up to 6.7%. The chip size is 0.80 mm×0.65 mm×0.05 mm．