Abstract: Time-varying gravity field is an important means to invert ocean mass change. A thorough evaluation of post-processing strategies of time-varying gravity field is essential to accurately obtain ocean mass change. This study adopted the gravity recovery and climate experiment (GRACE) and GRACE Follow-On (GRACE-FO) gravity field data to inverse the global ocean mass, evaluated the low degree coefficients replacement (C₂₀) and model corrections (including GIA, leakage) are evaluated, and quantified the contribution of different truncation degrees in ocean mass. The results showed that the stability of the original C₂₀ is poor, with the ocean mass change rate derived from it slightly higher than that obtained from independent C₂₀ coefficients based on SLR data. Therefore, it’s suggested to replace the original C₂₀ by using the C₂₀ provided by Goddard Space Flight Center (GSFC). The differences in correction values of the five GIA models are obvious, of which the correction derived from the Caron18 model is the largest. For the leakage correction, as the Buffer Zone extends, the ocean mass change rate increases. We find that the leakage is serious for the sea area less than 300 km from the coastline. Thus, a Buffer Zone extending at least 300 km beyond the coastline is preferred. From the perspective of contribution of different truncation degrees, it is found that when the truncation order is below 30, the estimated rate of change in ocean mass and the annual amplitude show significant differences, indicating that the coefficients below the 30 degrees have a non-negligible contribution to the inversion of ocean mass. When the truncation degree is 40, the cumulative trend and annual amplitude contribution reach to 98.56% and 98.79%, respectively. Thus, the contribution of the truncation degree mroe than 40 is quite small.