Similar to the analysis of Turbo codes, the parallel concatenated systematic polar code (PCSPC) can also be analyzed by the extrinsic information transfer (EXIT) chart. The convergence of the iterative decoding based on soft cancellation (SCAN) and belief propagation (BP) of PCSPC are analyzed by the EXIT chart. Analysis shows that SCAN decoder is more appropriate than BP decoder for this iterative decoding structure in terms of complexity. In addition, the weight coefficients of the iterative decoding structure are optimized by the simulated-EXIT (S-EXIT) chart, which improves the performance of PCSPC.