Geometric prediction merge mode (GPM) is a new tool introduced in the inter-prediction of Versatile Video Coding (VVC), which uses non-rectangular block partitions for coding unit (CU) partition to improve coding performance. To address the problem of large computational redundancy in the geometric prediction merge mode with motion vector refinement (GPM with MMVD), in this paper, a new decision algorithm is proposed based on CU gradient. By analyzing the characteristics of the CU using GPM, it has been found that there is a significant difference in the pixel values of the CU using GPM and the GPM partition mode is closely related to the CU texture boundary. By comparing the mean value of the gradient in four directions to determine whether GPM can be terminated early. The advance decision of GPM partition mode can be determined by the calculated gradient direction of CU. Experimental results show that compared with the VTM8.0 reference algorithm under random access (RA) configuration, the proposed algorithm can reduce the coding time by 13.5% on average, and increases the BD-rate of Y, U, and V components by only 0.14%, 0.13%, and 0.31% respectively.