A new formula together with the computing method for calculating Madelung constant α is given, based on the parallelepiped neutral cells which are situated around the reference cell,of which 26 such cells constitute the first shell and 98, 218,…,24 N2+2 cells constitute the second, third,…, and the Nth shell respec tively. The α(N) is a rapidly converging series and can be calculated very easily. In this paper Madelung constants and madelung energy for some complex io nic crystals have been computed by this new method which can be applied to all k inds of complex ionic crystals of trigonal ,orthorhombic system and so on.