Abstract: The low-noise amplifier is characterized by small noise figure and low output power. The characteristic of power amplifier is large output power and large noise figure. In order to achieve amplifier with small noise figure and large output power,the paper, combined with the design methods of low-noise amplifier and power amplifier, designs a low-noise power amplifier for harmonic radar transmitter. The amplifier consists of two-stage amplifier. The first stage amplifier achieves low noise and the second stage amplifier achieves power gain. The amplifier reaches more satisfactory results by optimizing the simulation design.The amplifier has good linearity and second harmonic suppression.