Abstract: In view of the multivariate regression analysis,astepwise regression analysis method with non-negative constraint to solve the ill-posed integral equation is proposed,which is required in NMR technique for the analysis of pore structure.This method is numerically stable,easy to implement with less calculations,and a more continuous distribution f(T₁) can be obtained.Two ways to reduce the effect of noise are suggested:Marquardt method and the smooth approach proposed by Hesse.From the results of the computed examples this method works quite well.