The invention discloses a power synthesis type power amplifier and a millimeter wave chip. Compared with the power amplifier in the prior art, the power amplifier provided by the invention comprises aDC power supply, N paths of sub power amplifiers, N matching circuits, an isolation circuit and N strands of transmission lines with lengths of 1/6 wavelength. Radio frequency signals input by the sub power amplifiers are output from drain terminals of transistors after being amplified by the transistors, matching circuits match the output impedance of the sub power amplifiers to load values required by the maximum output power, then the isolation circuit isolates the output signals of the matching circuits, finally impedance transformation and power synthesis are realized by the transmissionlines, and the synthetic power is output to the load. Therefore, the power amplifier provided by the invention can not only achieve port isolation and improve the performance of the circuit; and moreover, the lengths of the transmission lines are 1/6 the wavelength, thus reducing the area of the chip, reducing the loss and improving the power synthesis efficiency.