This paper is studied the effect of load representation, in the static point of view, on the performance of a UPFC connected in power system. The UPFC performance include the estimation of the UPFC control variables and converters powers that required to achieve certain operation condition, the lines power flow, the node voltages of the line at which, UPFC is connected, the total system power loss and the system voltage stability. Also the effect of load representation on UPFC optimal placement has been illustrated.