Abstract: A math method calculating the surface tension, the volume of liquid drop and the contact angle of a liquid drop on a level substrate is worked out in this paper. The method is carried out by computer according to the projection sizes of the liquid drop which was measured by the Chatel's method. The BASIC program fitting in single board computer type ZX-48 is Compiled. The surface tensions of Hg, Cu, Cu (40%)-Sb, Sb have been calculated with this program and the feasibility and the reliability of this method have been proved.