A GPU(graphic processing unit) based 5G software radio quasi cyclic LDPC (low-density parity check) code decoder was proposed. In order to save on chip and off chip bandwidth, code word shortening and punching techniques, two-stage quantization, and data packaging schemes were adopted to improve the utilization of data bandwidth. The experiment was based on the Nvidia RTX 2080Ti GPU platform to achieve parallel decoding of minimum and approximate decoding algorithms under high bit rates. By analyzing the optimal thread settings on the GPU, the decoding throughput of the 5/6 (2 080,1 760) LDPC algorithm is improved to 1.38 Gbit/s, and the decoding throughput performance is better than other GPU based LDPC decoders.