This paper firstly exhibits digital signal processing algorithm in a parallelization method with matrix representation. A two-stage iterated parallel digital filtering algorithm is expressed based on tensor product. Then a multi-stage iterated parallel algorithm is composed of two-stage algorithm, and a polyphase algorithm is conducted in order to enhance the parallel ratio. A 16QAM signal with 5 Gbps code rate is paralleled to 32 routes with the above algorithm and simulated in MATLAB. The simulation results show that the parallel algorithm is equivalent to the serial algorithm. Finally, the bit error rate is obtained, and the error between the theoretical bit error rate and the simulation results is within 0.05 dB.