An improvement over the method of pore size distribution analysis has been made in this work. The improved method is based upon the idea of the micro pore analysis of Mikhail, Brunauer, and Bodor, and utilizes the V-t curve of nitrogen adsorption. Two pore models are assumed, and the deviation of the initial slope of the V-t plot is ascribed to the pore filling and to the adsorption on the wall of unfilled pores. The improved method of this work is very convenient in that the analysis starts from the small pore regions. The method of this work is however quite distinct from the similar V-t plot method proposed by Sellevold and Radjy. The proposed method is applied to a few adsorbents, and very satisfactory results are obtained. The cumulative surface area calculated by this method also agrees very well with those obtained by the BET plot or by the t-method.