Aimed at the problem that inadequate numbers of measuring points can not acquire the propagation process of shock wave overall and the limitations of empirical formulate for overpressure and the low?accuracy?of numerical simulation, this paper utilizes the actual data to fit resconstruction of shock ware overpressure filed based on B-spline interpolation and the result is better than the reconstruction based on Delaunay triangulation and least?square?method. The isobars and 3D distribution of explosion overpressure filed simulated?by the Matlab are given out.The inversion results of the proposed resconstruction verified by actual measurement experiments shows that?the?errors?are within?4.5%.