Numerical analytic continuation is, in general, an ill-posed problem and some special regularization methods are needed. In this paper we apply the approximate inverse method to deal with the problem in a strip domain Ω={z=x+iy∈C∣x∈R,0<∣y∣<y0} in complex plane, the data is known approximately only on the line y=0. Error estimate between the exact and approximate solution with regularization parameter selected by both a priori and a posteriori strategy are provided, respectively. Numerical results show that the method works effectively, and can be a competitive alternative to existing method for the problem.