In line power flow regulation, in order to solve the problem that UPFC bus point voltage and DC capacitor voltage fluctuation, by setting up UPFC mathematical model, current decoupling controller of parallel converter are designed, according to the principle of power balance, the current feedforward compensation of voltage stabilization control is derived. and an improved coordinated control strategy based on shunt converter is proposed. The obtained feedforward compensation amount is introduced into the active and reactive power control system of the parallel converter，in order to realize unit feedforward, the methods of moving feedforward compensation points and adding feedforward compensation functions are adopted to improve the compensation effect during power flow regulation.. MATLAB is used to build a simulation model of 500KV AC transmission system with UPFC, the results show that compared with the coordinated control strategy before improvement, the proposed control strategy not only meets the requirements of coordinated control of active and reactive power flows, but also improves the voltage supporting capacity of the transmission system (the fluctuation of access point voltage and DC capacitor voltage has been reduced to 6.7 KV and 1.1 KV respectively), the response time of the system to the output of DC capacitor is also shortened by 0.5s.