The invention discloses a preparation method of a silver-based catalyst for degrading VOCs. The preparation method comprises the following steps: soaking an activated carbon fiber plate into a methanol solution, carrying out washing and drying, then, soaking the activated carbon fiber plate into a NaOH solution, and drying the activated carbon fiber plate; placing the obtained activated carbon fiber plate into a mixed solution of (NH4)2C2O4.H2O and KMnO4, adding hydrochloric acid to regulate the pH of a mixed system, then, placing the mixed system into a constant-temperature oil bath pan, carrying out stirring for a reaction, then, taking out the activated carbon fiber plate, and carrying out washing and drying; adding an ammonia solution into an AgNO3 solution, and carrying out stirring until the solution becomes transparent; soaking the obtained activated carbon fiber plate into the transparent solution, adding an H2O2 solution, and carrying out stirring; and finally, taking out theactivated carbon fiber plate, and carrying out washing, drying and calcining to obtain an Ag/MnO2-ACF catalyst. By using the method, the relatively strong VOCs adsorption is realized, meanwhile, the degradation rate and mineralization rate of VOCs are greatly increased, and the stability is also improved.