The electronic density of states is the number of states in the unit energy range.It is a physical quantity closely related to electronic energy band structure.In order to calculate the specific heat of electrons and the transport properties of crystals,a more accurate method must be used to calculate the electronic density of states.The processing of this in general textbooks usually adopts simplified models,which does not reflect the calculation ideas of states density in general.In this article,two-dimensional graphene and three-dimensional face-centered cubic lattice are explained in detail based on the formula of electronic density of states.The calculation steps of the density and a detailed explanation based on numerical calculation are given.