Abstract: Dual-band power amplifiers have been one of the hot spots in 5G research. When dual-band excitation signals appear at the same time, the traditional dual-band power amplifier will deteriorate the impedance matching due to the modulation effect produced by the dual-frequency signal, even mismatch occurring. For the problems mentioned above, a power amplifier with a balanced structure is proposed which can work at GSM 900 and TD-LTE band. thus continuously optimizing its matching degree, and the reflection component caused by impedance mismatch is eliminated by dual frequency coupler, thereby the impedance mismatch caused by modulation effect can be improved largely. Firstly, this paper is based on π-type impedance transform structure , which design a concurrent dual-band 3 dB directional coupler. In addition ,in order to avoid the cumbersome calculation of the dual-frequency impedance converter and difficult space layout, the branch amplifier circuit adopts a dual-frequency impedance converter model combining π-type and T-type. Through theoretical derivation and simulation of power amplifier, this structure can realize different impedance transformations at any frequency. Finally, the power amplifier can be applied in both GSM900 and TD-LTE at the same time. The design is based on the ADS simulation platform, and the GaN transistor CGH40010F is selected for the design simulation. Meanwhile, the Rogers 4350b sheet is used to make a material object. The measured results show that it can match with 900 MHz and 2.6 GHz frequency bands very well, compared with traditional concurrent dual band power amplifier, the power amplifier structure proposed in this paper can optimize the matching performance significantly, and the VSWR has been reduced effectively. Saturated output power is 44.6 dBm and 43.3 dBm. Compared with the single power amplifier, the saturated output power has doubled. The PAE on the two working frequency bands is 62% and 64%, respectively, where is a small gap between actual measurement and simulation, which has good consistency. By analysis and test, the power amplifier can adapt to the development needs of wireless communication systems well .