Abstract: This paper is the continuity of the reference [1] and [2], is also last a paper of those works. Its subject are to solve the equations of the primary electrons with Lagranican method.At the same time,numerrccal results are given by PIC, Eulerian and Lagrangean method. we compare those results with the results of the non-self-consintent method when electric field intensity E>10⁵v/M,the results of the self-consistent method is nearer when electric field intensity E≤10⁵v/M, the results of self-consistent rather nice coincide with the results of non-self-consistent method.