The invention relates to a preparation method of a nitrogen-doped porous carbon material, in particular to a method for preparing the nitrogen-doped porous carbon material with casein as a carbon source and a nitrogen source, and further relates to application of the nitrogen-doped porous carbon material in a super-capacitor and electrochemical performance of the nitrogen-doped porous carbon material. The preparation method is convenient and environment-friendly in raw material source, and is a new way to prepare the nitrogen-doped porous carbon material by using biomass, the preparation stepis easy, the reaction condition is relatively mild, operation and control are easy, and the prepared nitrogen-doped porous carbon is large in specific surface area and high in specific capacitance. The specific surface area of the super-capacitor electrode material prepared under good conditions can reach 1902.5 m<2>g<-1>, the nitrogen content can reach 8.3%, in a 6M KOH solution, under the current density of 1Ag-1, it is measured that the specific capacitance can reach 393.2 Fg<-1>, the cycle stability is good, and a relatively ideal super-capacitor electrode material is achieved.