Abstract: By the related results of WZ theory and the residue theorem,with the help of computer algebraic system,a kind of solution for the following problem are obtained:for any given ,how to construct functions g(t)、g(t,s) (where sS R ),different from f(t) in essence ,so that g(t)=g(t,s) (e.g. s=1 )and , . From the above result, either some new integral formulas or a simple but new proof for some known integral formulas can be found and generalized.In particular,the identity is proved and generalized,which wad obtained by Cadwell in 1947 by using contour integration.