Abstract: Capillary pressure curve is considered to be the most effective way to evaluate reservoir pore structure and initial oil saturation of reservoir. Based on the analysis of the morphologic characteristics of capillary pressure curves thoroughly, a new method to obtain capillary pressure curve at point - to - point was presented using the permeability of sandstone. This method was available in various types of reservoirs. Using this constructive capillary pressure curves, the initial oil saturation of reservoir can be e-valuated consecutively. Compared with the oil saturation which was gained by well logging interpretation, the absolute error was 1. 46% and the fractional error was 2. 5%.