Abstract: Gravitational potential can be expressed as a mathematical series,in which the firstsection is geoid potential-W0.This method was used to determine the Baltic Sea geoid poten-tial by using the GPS station data(1997-04).The results show that the first rank term com-puted by EGM2008is almost equal to the results computed by WGD2000(complete to degreeand order 360)while the difference is about a quantity of 10-3.The second rank term has aquantity of 10-5and can be omitted.In the case of changeless geocentric coordinates,the de-termination of W0is largely affected by changing height data,so it is important to accuratelydetermine the height of the GPS station.The W0value(62 636 857.23±０．４８ｍ2·s-2)ofBaltic sea study site is obtained by using five set of GPS stations and an EGM2008modelwith degree and order of 360.