A calculation method of microdosimetrical quantities epsilon D and yD using the proximity function t(x) of the delta rays of an incidental radiation is introduced. In comparison with classical Monte-Carlo calculation, the presented method is simpler and faster. Therefore there is the possibility to calculate effectively the microdosimetrical quantities in a large scale of the dimension of the volumes from 10(-9) to 10(-6) m and for various energy spectra of ionizing particles of a different kind. The presented method was verified low energy electrons and X-ray. Our results are in good agreement with published data.