Abstract: Currently reactive power compensation strategies of CSP-PV hybrid system are mainly controlled independently for CSP power station and PV station. and there is a lack of coordinated control mechanism between them. The aim of the proposed work is to present a coordinated optimal control strategy of reactive power on CSP-PV hybrid system,which contains three parts. First,the reference values of reactive power are estimated by monitoring the voltage of central point. Second,the optimal reference values of reactive power for each power station at each point of common coupling（PCC）are calculated by DE-PSO algorithm. Third,reactive power distribution of equipment in the station is completed based on the principle of reactive power distribution. The simulation results show the control strategy fully utilizes the reactive power control capability of the synchronous generator,the photovoltaic inverter and the reactive power compensation device,which realizes the optimal distribution of the reactive power compensation task in the CSP-PV hybrid system,and improving the system integration bus voltage stability and reduces the network loss.