The invention provides a preparation method of an AKD paper sizing agent. The method comprises the following steps: (1), dissolving HAuCl4 and PVP-DADMAN into water, boiling the water, then adding a reducing agent, keeping the HAuCl4 and PVP-DADMAN in dark place, stirring to make the HAuCl4 and PVP-DADMAN react, performing centrifugation, and performing vacuum drying on supernate, so as to obtainmodified nanometer gold particles; (2), dissolving PEOS into molten AKD, and taking the PEOS as an oil phase; dispersing the modified nanometer gold prepared in the step (1) into water, adjusting pH to be acidic, and taking the modified nanometer gold as a water phase; performing ultrasonic mixing on the water phase and the oil phase while heating, and allowing the water phase and the oil phase tostand still, so as to obtain oil-in-water type AKD Pickering emulsion, namely the stress induced AKD paper sizing agent. The sizing agent effectively reduces coalescence of AKD oil drops, greatly improves the stability of emulsion, ensures that water phase and oil phase are not separated out after the emulsion is stabilized for a plurality of months, does not need to add any surfactants and othermodifiers, and is simple in structure and easy to operate.