An inverse reconstruction investigation is presented to determine the inner boundary location(corroded point)of heat transfer composite walls from measurement data on the exterior boundary.The Finite Block Method(FBM)is developed in this paper to solve transient heat problem across multilayer composite walls.Starting from one dimensional problems,Lagrange series interpolation is used to create the first order differential matrix and higher order differential matrices can be obtained afterwards.Combining with mapping technique,the physical domain is mapped into a normalized domain for both two-dimensional and three-dimensional problems with 8 seeds or 20 seeds respectively.Both time-spatial approach and Laplace transform with Durbin inversion are employed and compared in the paper.Three numerical examples are presented to demonstrate the accuracy of FBM.Comparisons have been made with Finite Element Method(FEM)and Point Collocation Method(PCM)with radial basis functions respectively.It indicates that FBM is of higher degree of accuracy even with quite a few collocation points.In addition,FBM has high stability at different levels of perturbation in measurements.