This paper presents a optical cross correlation system which uses a microcomputer to collect and process data for average velocity measurement of particle cloud in an air suspension. A contactiess measurement of a moving particle velocity can be obtained by determining the position of the peak of the cross correlation function of two attenuated laser beams. The experiment results show that the tecnique of correlation of optica intensity fluctuation can be used as an efficient tool to measure flow velosity in two-component fluids.