Based on the intersection between Gauss electron beam and the largest cross-sectior of the particles, a method is proposed for calculating the X-ray intensity emitted frond particles. The intensity of the characteristic X-rays from particles of the shape of spheroid, cuboid, elliptic cylinder or elliptic spheroid has been calculated for Al, Cu and Au at 20keV and 25keV. Monte Carlo evaluation of the electron scattering was performed using the model put forward in reference (1).