Abstract: The zero drift and its linearity are the most important performance indexes of gravimeter and also considerably dominate the instrumental accuracy and lifetime. Based on an analysis of drift data from 14 CG?5 gravimeters, the authors found that the average drift rates of the majority of instruments are between 0.7 and 1.7×10-5 m/s2/day in two years. On such a basis in combination with the relat?ed data provided by manufacturers, the service lifetimes of CG?5 gravimeters have been inferred in this paper. The normal mean opera?tional lifetime seems to be about 10 years in the area of forty degrees north latitude.