Abstract: GPS coordinate time series show significant seasonal variations. We here study the vertical coordinate time series of 233 GPS stations in Crustal Movement Observation Network of China (CMONOC). Based on the root mean square (RMS) reduction ratio of coordinate time series with and without the environmental loading corrections, we quantify the improvements of CMONOC coordinate time series with the corrections of different environmental loading products provided by Helmholtz Centre Potsdam - German Research Centre for Geosciences (GFZ) and EOST. The statistical results show that the RMS of 90.2% and 75.54% of the stations are reduced after the correction of the environmental loading product provided by GFZ and EOST respectively. It shows that the loading products of GFZ have better performance to explain the non-linear variations of the verticals than those of EOST. It is also found that the environmental loading corrections not only have a significant improvement effect on the seasonal part of GPS verticals, but also on the non-seasonal part. After the loading correction of GFZ, the annual amplitude of 87.8% of GPS stations is decreased, and the RMS of the non-seasonal part of 82.4% of the stations is reduced.