The invention relates to a metal matrix composite material technology and aims at providing a high-elongation-percentage silver-based electric contact material and a preparation method thereof. The raw material formula is composed of, by weight percent, 84%-88% of silver powder, 1%-8% of silicon carbide whiskers, 2%-6% of copper fibers, 1%-12.9% of nanometer silica sol and 0.1%-1% of a surface modification agent. By means of modification of the nanometer silica sol, a continuous network structure is formed in a silver matrix, good properties of the silicon carbide whiskers and the copper fibers are brought into full play, the elongation percentage, the conductivity and the tensile strength of the silver-based electric contact material are improved, and therefore the defects that an existing environment-friendly silver-based electric contact material is poor in machinable property, high in electrical resistivity and the like can be overcome. The silver-based electric contact material is environment-friendly in preparation process, easy to operate and low in cost. Under the condition that the same performance is achieved, the using amount of silver in the electric contact material can be reduced, and therefore precious metal resources are saved.