Abstract: The data for state estimation are measured by wide area measurement system (WAMS) and supervisory control and data acquisition (SCADA) currently, and the optimal placement of phasor measurement unit (PMU) in WAMS system becomes key research aspect. In this paper, based on the analysis of differences on data composition, time section, accuracy and refresh rate for WAMS/SCADA hybrid data measuring, an effective compatible scheme is realized, and a PMU optimized placement strategy is proposed based on dynamic state estimation by unscented kalman filter (UKF) and discrete particle swarm optimization (DPSO) algorithm. By applying hybrid measurement data to estimate UKF dynamic state, precision of state estimation is improved greatly. The simulation results of daily load changes in IEEE 39-node system verify the validity of this PMU placement scheme.