Abstract: In the solid millimeter-wave power amplifier design, the output power of a single MMIC is limited, so the power combiner technology was used in the power amplifier to improve the output power of the power amplifier system. Now,the difficulty of the design of power divider/combiner is improved the isolation between each branch. A high isolation of the 3 dB power divider structure is proposed by the analysis of the traditional magic T, and the power amplifier MMIC chip can be protect in this system. The results of the experiment show that the isolation between the two branches is up to -42dB in 29.3 ~ 39.3GHz, and the insertion loss of the branch is more than-0.35dB, which meet the requirements of practical application.