In order to research surface characteristics of liquid metal which based on hydrodynamics theory and interaction principle between laser wave and surface tension stationary wave of liquid metal,it is finished to provide an entirely theoretical equation,apparatus and techniques of the measuring the surface tension for liquid metal at high temperature.This apparatus is an automatic measuring system for in formation collecting and processing,in which a computer is attached to charge coupled device,driving circuits and A/D converter.Applying the new apparatus the surface tension values of Sn-Pb based binary and ternary alloy solders have been obtained on the basis of the above work.The experimental results indicate that the surface tension values of liquid metal Sn-Pb based solders are decreased by37.3% and 31.9% respectively.When 1% of Bi or In is added in the solders,the elements Bi and In have evident surface activity in Sn-Pb based solders and the wettability of the solders in increased with increasing surface activity.