To enhance the power supply capacity and solve the problem for UHVDC power assumption of 500 kV power network in Suzhou,the feasibility research on the application of UPFC in 500 kV Southern Power Grid of Suzhou is carried out.Combined with the scheme of UPFC integrated and its topology structure,the capacity of UPFC is determined by system calculation and the principle for the key parameters selection of UPFC main equipment are supplied.The effect of UPFC on the power flow and voltage regulation of 500 kV power grid in southern Suzhou is verified by simulation,which indicate that under the heavy load condition of Suzhou power network in winter,the regulation of UPFC can eliminate the key section overload problem as N-1,while under the heavy load condition in summer,it can decrease the capacity of load shedding as the UHVDC bipolar blocked.The reactive power control of UPFC can provide the dynamic voltage support for power grid,which is benefit to decrease the probability and duration time of commutation failure of UHVDC.