The invention provides a glass fiber soakage agent for reinforcing ABS plastic and AS plastic and a preparation method of the glass fiber soakage agent. The soakage agent is prepared from a coupling agent, a lubricating agent, an antistatic agent, a pH value adjusting agent, a film-forming agent and deionized water, wherein the film-foaming agent is prepared from a styrene-butadiene rubber latex, a styrene-acrylic emulsion and a nonionic polyurethane emulsion, and the film-forming agent accounts for 2.0%-20.0% by mass of the soakage agent. The preparation method of the soakage agent comprises the steps of pre-dispersing the coupling agent, pre-dissolving the lubricating agent, pre-diluting the film-forming agent, preparing the soakage agent and the like. By means of the soakage agent, the physical and chemical properties of the surfaces of glass fibers can be changed, the glass fibers are good in bundling, the compatibility of the glass fibers with the ABS and AS plastic can be effectively improved, and produced AS and ABS plastic products have the advantages of being high in impact strength, good in product appearance, long in service life and the like.