The invention discloses a fiber mat, comprising 50-100 (weight ratio accounting for the dried fiber mat and the same below) glass fiber and chopped strands, and one or more of 0.1-30 inorganic fibers, 0.1-30 natural fibers, 0.1-30 synthetic fibers, 0.1-30 manmade fibers and an anti-radiation material besides the glass fibers and the chopped strands. The fiber mat is prepared by a needle punching method, a spun lacing method, a thermal rolling method, a wet type paper-manufacturing acid process, a wet type paper-manufacturing thickener method, a wet type paper-manufacturing gel method and the like. According to the preparation method for the fiber mat disclosed by the invention, the conductive thermal coefficient of a vacuum thermal insulation plate made of the fiber mat achieves 25-65% under the premise of adopting the same production mode, and a more superexcellent thermal insulation effect is obtained.