The invention belongs to the field of preparation of electrocatalytic hydrogen production catalytic materials, and particularly relates to a preparation method of a nickel oxide-loaded sulfur- and phosphorus-doped graphene composite electrocatalyst, which comprises the following steps: uniformly mixing graphene oxide, phosphoric acid and sulfuric acid to form an aqueous solution, and transferringthe aqueous solution into a hydrothermal kettle for hydrothermal reaction to obtain sulfur- and phosphorus-doped graphene; and uniformly mixing the sulfur- and phosphorus-doped graphene, nickel chloride hexahydrate and ethanol, carrying out hydrothermal treatment on the mixture, and carrying out suction filtration, washing and drying on the obtained solution to obtain the nickel oxide-loaded sulfur- and phosphorus-doped graphene composite electrocatalyst. The method is simple in reaction condition, convenient to operate and short in technological process; and the prepared nickel oxide nanosheet is good in dispersity and proper and uniform in size, and has excellent hydrogen evolution performance when used as an electrocatalytic hydrogen evolution electrode catalyst.