The dataset contains the monthly mass-term sea level variations in the South China Sea from 2005 to 2015. Five datasets were used to calculate the mass-term sea level variations: the GRACE Spherical Harmonics (noted SHC), the GRACE Mascon solutions (noted Mascon), the GRACE Slepian Function solutions (noted EST), ECCO Ocean botton pressure model (noted ECCO), and steric-corrected satellite altimetry dataset (noted AsS). Besides, the signal (with trend, seasonal and semi-seasonal information) and the residual mass-term sea level was given separately. The boundary of the South China Sea and the longtidue and latitude of the study area were also given. Please noted that the longitude and latitude of the steric-corrected satellite altimetry dataset was different from the other four. For further information about the Slepian function method, please refer to our released code: https://github.com/KMartin0013/Slepian_ocean_add-on.git If you use this dataset, please cite our work properly: Zhongtian, Ma, Hok Sum Fok, Robert Tenzer, Jianli Chen. A Novel Slepian Approach for Determining Mass-term Sea Level from GRACE over the South China Sea. Int. J. Appl. Earth. Obs. Geoinf., 132, 104065, 2024. doi:https://doi.org/10.1016/j.jag.2024.104065