The invention discloses a two-dimensional traveling wave high-gain broadband CMOS power amplifier, which comprises an input power division network, a first input third-order artificial transmission line, a second input third-order artificial transmission line, a drain bias network, a first high-gain two-pile PMOS amplification network, a second high-gain two-pile PMOS amplification network, a third high-gain two-pile PMOS amplification network, a first high-gain two-pile NMOS amplification network, a second high-gain two-pile NMOS amplification network, a third high-gain two-pile NMOS amplification network and an output two-dimensional three-order artificial transmission line network. The core architecture adopts the characteristics of high power and high gain of the high-gain two-pile PMOS and NMOS amplification networks in the microwave band, and meanwhile, the ultra-wideband frequency response characteristic and the simplified series voltage division structure of the two-dimensionaltraveling wave amplifier structure are utilized, so that the whole power amplifier obtains good wideband, high gain, high efficiency and high power output capability, and a power supply network is simple.