The invention discloses a preparation method of a nickel hydrogen carbonate-polydopamine-graphene composite material. The preparation method comprises the following steps of providing graphene oxide;preparing a graphene oxide suspension liquid with concentration being (0.5-2) mg/mL with ultrasound; heating the obtained graphene oxide suspension liquid to 60 DEG C, adding dopamine hydrochloride, performing reduction and surface polymerization on graphene oxide by employing the dopamine hydrochloride to obtain a polydopamine-graphene compound; dispersing the polydopamine-graphene compound in deionized water to prepare a polydopamine-graphene suspension liquid with concentration being 5mg L<-1>; adding a nickel salt and a precipitant, performing hydrothermal reaction, and performing centrifuging, washing and vacuum drying to obtain the composite material after reaction is completed. The composite material provided by the invention has favorable electrochemical performance in a KOH electrolyte, excellent specific capacitance in a three-electrode system is achieved, and the specific capacitance reaches 2,068F g<-1> under a condition of 0.8A g<-1>.