This invention disclose silver - nanometer tin oxide contact material and their, and preparation of the electrical contact materials SnO2 the weight percentage of 8 to 12 percent, with an average particle size of less than 100 nanometers, but also a 0.1 to 1% CuO, MS volume Ag. Preparation of its major include: stannic chloride and citric acid solution was prepared by adding ammonia Sn (OH) 4 hydrosol; Ag powder dissolved by adding ammonia from AgNO3 solution after mixing uniform joined Sn (OH) 4 hydrosol, sprayed the hydrazine hydrate reaction after cleansing, concentration, drying in the Ag-Sn (OH) 4-coated powder; coated milling and baking powder, as treatment with Ag powder mixture and processing; in the Ag-nanometer SnO2 powder processed by a conventional process, Contact Materials. Silver Powder used by the copper powder can be added to the Ag-Cu-Sn (OH) 4-coated powder. This process Sn (OH) 4 Sol a good dispersion, coated Ag, calcined SnO2 particles dispersed in the matrix of Ag, income, life expectancy and electrical contact materials tensile strength, hardness has risen markedly, and the stability and processing sexual better.