Abstract: In order to improve the efficiency of Digital TV transmitter, a new type of threeway Doherty circuit is used. Based on the transmission line theory and active loadpull theory, this paper deduces the principle of the threeway Doherty, and with ADS to design a double threeway Doherty power amplifier and applicated it in the Digital TV transmitter. The simulation result shows that the amplifier reaches its first peak efficiency at the backoff 9.1 dB; and has three peak efficiency points at the whole backoff power range. And the measured result shows that, at 610 MHz frequency, the amplifier’s efficiency can reach 41.2% with 54dBm output power. 