This paper presents a new numerical solution for Neumann problem of Helmholtz equation in R~ 3. The expression of the solution for this problem is obtained by use of a double layer potential and it leads to a Fredholm boundary integral equation of the first kind. 本文给出一种三维Helmholtz方程Neumann问题的新的数值解法。首先利用双层位势推得问题解的积分表达式并导出了一个Fredholm第一类积分方程。