Aerosols play important role in weather. The Rainfall amount is affected by the soot aerosol that is available in the air of cities, especially industrial and populated cities. Hence, with the formation of artificial cloud in the laboratory through quasi-adiabatic expansion, some results investigated. In addition, a method based on time variations of the laser beam through the cloud droplets used to estimate the size distribution of the cloud droplets. In this experiment, soot aerosol injected into the cloud with different concentrations and the results of cloud formation in presence of compared with the result of background aerosols. The results showed that if soot particles presents with low concentration in the atmosphere, more droplets and with larger radius form in the cloud. However, with increasing soot concentrations, the radius of the formed droplets decreases. Thus, the probability of precipitation decreased.