Light intensity distributions of two typical lamp2houses used in Laser Particle Counter System (LPCS) ———He2Ne laser and semiconductor laser are measured by Beam Profile2350. According to the results , intensity uniformity of sensitive volumes formed by two lamp－houses respectively is analyzed. Using the LPCS ,the particle size distributions of the normal particles are measured and corresponding counting efficiency and distinguishability are calculated. The results indicate that intensity uniformity of sensitive volume formed by semiconductor laser is better than that formed by He－Ne laser ,and correspondingly , the former has better counting efficiency and distinguishability. By comparision with using He2Ne laser , LPCS using semiconductor laser can make its distinguishability of particle diameters increase 17 %.