Abstract: According to the thorough research of computerized tomography (CT) in medical field, there are different scan methods for different kind of objects. There isn’t any interval between two topographies. The CT image processing software is usually applied in a workstation. When CT is used into the wood industry, in order to improve efficiency and reduce cost, the interval between two topographies is expected so that the data of CT image can be reconstructed by PC. However, the research about this method of interval and interpolation hasn’t been reported yet. This article, based on the reconstruction of three-D data by cubic natural spline function, compares the data got by using interval interpolation and that got without interval, and the result doesn’t show much difference between these two groups of data. The application of cubic natural spline function can reconstruct three-D data and thus improve efficiency and lower cost.