The scattering pulse signal counting distribution generated by the irregular particle is the full reflection of particle size distribution. On the basis of two parameters-amplitude and width,the statistic characteristic of the random pulse signal is studied. The laser particle counter photoelectric sensor is used to measure the amplitude and width of the scattering pulse signal which is generated by the aerosol particles in air. The experimental results indicate that the statistical distribution of the pulse signal is not axis-symmetrical but lognormal distribution which is a specific exhibition of the random effects in measurement. It shows that it has fractal structure relation among the characteristic parameters of the non-spherical particles. In particular,the fractal dimension is the statistical dispersion′s ratio of the amplitude and width of the scattering light pulse.