Abstract: A method of measuring the porosity of the nuclear membrane was described. The nuclear membrane was irradiated vertically by the collimated monoenergetic alpha rays, and the energy spectra were obtained on the other side. The porosity values were got through the analysis of the alpha spectra. The porosities of 30 sets of nuclear membranes were measured with both alpha spectroscopy and microscope analysis technique, and the results were analyzed and compared. The results from the two different methods agree with each other very well within the measurement error, and it means the alpha spectroscopy method is feasible.