The invention provides a preparation method of zinc dialkyldithiophosphate and application of hydrogen peroxide. The preparation method of the zinc dialkyldithiophosphate comprises the following steps: (A) adding base oil and/or a small amount of zinc dialkyldithiophosphate, zinc oxide and hydrogen peroxide, and stirring; and (B) adding dialkyl dithiophosphoric acid to react, and filtering to obtain the zinc dialkyldithiophosphate. The hydrogen peroxide shows a good promoting effect in the preparation process of the zinc dialkyldithiophosphate, and decomposition products are water and oxygen,so that the decomposition products are easy to separate from a target product and free of residues. The process for preparing the zinc dialkyldithiophosphate (hereinafter referred to as ZDDP) by taking the hydrogen peroxide as a saponification accelerant has the characteristics of easiness in product filtration, less filter residue, light color, high pH value, good thermal stability and demulsibility, high zinc oxide utilization rate, greatly improved product quality and yield, greatly reduced waste residue and obviously improved production benefit.