The invention discloses a preparation method and application of a sulfhydryl bagasse solid-phase extraction agent. The preparation method comprises the following steps: mixing thioglycolic acid, tetrahydrofuran and concentrated sulfuric acid uniformly to obtain a reaction solution, adding pretreated bagasse into the reaction solution, standing the reaction solution at the temperature of 38-40 DEG C for 45-50 hours, filtering out the reaction solution, washing the filtering residue with deionized water until the filtering residue is neutral, filtering to remove water, adding absolute ethyl alcohol to wash off residual water, filtering to remove ethyl alcohol, and drying to obtain the sulfhydryl bagasse solid-phase extraction agent, wherein 40-60ml of thioglycolic acid, 40-60ml of tetrahydrofuran, 0.05-0.15ml of concentrated sulfuric acid and 8-12g of bagasse are used. The sulfhydryl bagasse solid-phase extraction agent can be prepared conveniently, efficiently, easily and rapidly, can be filled into a commercial solid-phase extraction column so as to dynamically enrich an actual water sample by using a solid-phase extraction device, can adsorb a various of metal ions in water efficiently and rapidly, has strong selectivity and good desorbing performance, can be repeatedly used for multiple times and is a practical potential heavy metal extraction agent.