FIELD: membrane filters based on nuclear track membranes. SUBSTANCE: membrane is placed in irradiation chamber, and it is irradiated by beam of particles accelerated in cyclotron. Separation of signals associated with pores is performed by measuring the energetic spectrum of particles passed through pores and directly through membrane film. Then areas of energetic peaks of particles passed through pores and membrane film are determined, and porosity is ground by their relation processing from expression, where N0 is number of particles recorded in section of energetic spectrum near maximum energy E0; N1 is number of particles recorded in section of energetic spectrum near minimum energy E1; N1 is number of particles recorded in section of energetic spectrum in intermediate area between E0 and E1. EFFECT: more effective determination of nuclear membrane porosity. 2 dwg.