In order to improve the detection performance and reduce the computational complexity of the parallel interference cancellation (PIC) algorithm in the multiple-input multiple-output (MIMO) system, a serial/parallel hybrid detection algorithm (HIC) was proposed in this paper by incorporating the serial interference cancellation (SIC) idea. The proposed algorithm first reduces the computational complexity by optimizing the common components of the different sub-detection processes in PIC, and then substitutes the estimated results of the sub-detection into the subsequent sub-detection to achieve hybrid processing to improve detection performance. The simulations results show that in a 4-QAM modulated MIMO system, the proposed algorithm has a performance improvement of about 1.2 dB compared with that of the traditional PIC algorithm when the bit error rate is . And the number of complex multiplications of the proposed algorithm is only about 28% of the traditional PIC algorithm.