Besides standardization, zero correction error constitutes the most common error source of a gravimeter. Based on data accumulated in high-precision gravity elploration carried out by the authors in recent years, this paper has made a comparatively comprehensive and objective analysis and investigtion: (1) analytical conclusions were drawn on normal zero variation and zero mutation character of Lacoste-Romberg gravimeter; (2)by employing dynamic and static separate procesiug technique for measured data, the paper analysed zero correction error resulting probably from zero nonlinear variation when the gravimeter works continuously from several to tens of days; (3)through analysis and calculation of measured data, the referential values concerning the effect of zero mutation upon observation precision of the gravimeter were obtained; (4) in accordance with the practical problems arising from the use of gravimeter, the measures for improving zero drift linearity wete proposed.