We analyzed the delay synchronization errors in Pecora and Carroll's chaotic self synchronizing scheme. The delay synchronization errors are simulated using the masking scheme of Lorenz chaotic system on computer. Given system parameters, the relational curves of the mean square error vs sampling step length are presented for different delay time. Given system parameters and delay time, the error curves of chaotic time series are given for different sampling step lengths. Given sampling step lengths, the scale changes of chaotic time series are obtained for different system parameters. And given delay time, the relational curves of mean square error vs sampling step length are shown for different system parameters. Then some ways of decreasing the delay synchronization errors are proposed. Some new results obtained in this paper are useful for practical applications of chaos synchronization and chaos control.