The characteristics of crustal deformation movement around the epicenter before the Aksai M5.5 earthquake in 2021 were studied in this paper. According to the GPS observation data provided by CMONOC, the characteristics of crustal deformation before the M5.5 earthquake were discussed by the GPS velocity field analysis, the area strain rate field analysis, and the baseline time series between stations. The results show that the epicenter of Aksai M5.5 earthquake is located in the southwest side of the seismogenic fault, where the far-field velocity is large and the near-field velocity is small, and the velocity field directions are obviously different on both sides of the seismogenic fault. It is also located in the high-value area of the compressive area strain rate field consistent with the type of seismogenic structure, namely the compressive strain accumulation area. The turning change of baseline length across the seismogenic fault more than 3 years before the earthquake indicates that the left-lateral strike-slip rate on both sides of the seismogenic fault decreased significantly before the earthquake. The acceleration of the compression rate on both sides of the fault reflects that the strain energy accumulated before the earthquake. The results can provide basic research data for understanding the seismogenic process of the Aksai M5.5 earthquake. Besides, it can provide a reference for the prediction of strong earthquakes in areas with similar structural types.