The morphology of nanomaterials can affect their electrochemical performance. It is a challenge to design metal oxide nanostructures with controllable morphology/size and good electrical conductivity for their application in electrochemical supercapacitors and other energy storage devices. NiMn2O4 electrode materials with different amounts of polyvinylpyrrolidone (PVP) were prepared by a co-precipitation method. The effect of PVP (0, 0.2, 0.4, 0.8 g) amount on the microstructure and capacitance properties of NiMn2O4 was investigated. The results show that the microstructure of NiMn2O4 changes from an agglomerated granular to loose flocculent and fine powder with the increase of PVP content. The optimum capacitance performance of NiMn2O4 can be obtained at PVP amount of 0.4 g, and the specific capacitance of NiMn2O4 is 1 464 F/g at a current density of 1 A/g. At PVP amount of 0.8 g, the excessive amount of PVP is easy to cause residue in NiMn2O4 in the cleaning process. During the electrochemical test, the amount of active substances involved in the redox reaction is relatively reduced, leading to the decrease of the capacitance performance of NiMn2O4-0.8. The specific capacitance is 1 010 F/g when a current density is 1 A/g.