PMU placement is important to achieve full system observability. Traditional PMU placement algorithms only work for systems in normal condition. During power system restoration, system topology and condition change in each step. Synchrophsors can help to improve the reliability and efficiency of restoration strategy. However, the original PMU placement cannot guarantee system observability in each restoration step. In this paper, a new optimal PMU placement is formulated for single and multiple islands restoration. With the aid of PMU, system operator can obtain real-time measurements of voltage (magnitude and angle) and frequency from different islands and perform the parallel restoration precisely. The proposed algorithm is tested in modified IEEE 14-bus system. Simulation results demonstrate the effectiveness of proposed model and the advantage of PMU-aided parallel restoration.