In order to improve the error-correction performance of polar codes with the medium and short code lengths, an improved successive cancellation list decoding algorithm based on the error set (ES-SCL decoding algorithm) of polar codes is proposed. The algorithm first constructs an error set according to the channel characteristics of polar codes. Then the parity check(PC) bits is set according to the elements in the error set during the encoding of polar codes and the information bits and frozen bits is placed in the remaining positions. When the decoder decodes the PC bits, each path don’t perform the path splitting and pruning, but can get the estimation of the PC bits through the check function. For the other bits, the decoder will directly does the SCL decoding. Simulation results show that under the additive white Gaussian noise channel, when the codes length is 512, the codes rate is 0.5, the block error rate is 10-5 and the maximum list length is 8, compared with the CA-SCL and PC-PSCL decoding algorithm, the proposed ES-SCL decoding algorithm can achieves a gain of about 0.18dB and 0.15dB .When the codes length is 256, the codes rate is 0.5, the block error rate is 10-5 and the maximum list length is 8, compared with the CA-SCL and PC-PSCL decoding algorithm, the proposed ES-SCL decoding algorithm can achieves a gain of about 0.3dB and 0.35dB. Furthermore, the ES-SCL decoding algorithm that uses the partial bit splitting decoding can reduce the sorting number of about 50% when the block error rate is almost the same as that of the PC-PSCL decoding algorithm, thus its decoding complexity is lower.