Abstract: This base line for calibrating gravimeters for seismological purposes was established by 18 high precision gravimeters in Nanking and Peking in May 1978. In this paper, the results has been combined with the data from related gravity comparative measurements. From the analysis of the factors causing the variations of scale values of the gravimeters and the errors of measurements thus procured, the importance and requirements for calibration of gravimeters have been discussed. Then the method and technique to select and to establish the base line for calibrating gravimeters for seismological work and the possible ways for reducing calibration error in order to increase the accuracy of gravity measurenents are proposed.