Abstract: There are two crucial steps in resolving semi-parametric model. One is to choose the regularizer, and the other is to determine the smoothing parameter. The emphasis of this paper is on the determination of the smoothing parameter. A new method for determining smoothing parameter, L-curve method, is investigated. On the basis of analyzing the basic theorem of L-curve, the authors realize its algorithm and apply it to the mitigation of systematic errors.Furthermore, we combine the L-curve with different methods to resolve the semi-parametric model and compare their results.