A linear high-efficiency Doherty Power Amplifier(PA) operating at 3.35 GHz is presented. The cancellation principle of the Third-order Intercept Point(IM3) in Doherty technique is adopted in order to improve the linearity of the proposed Doherty amplifier. The Doherty amplifier employs two 6 W GaN HEMT transistors namely CGH40006P from Cree to validate the proposed principle. The results shows that at the design frequency point 3.35 GHz, IM3<-30 dBc.