Abstract: The formation of precipitation in connective cloud with cell structure is investegated, based on the fact that a cloud consists of a great deal of cells in different phases. Considering that water content and speed of updraft in the cloud cells are larger than that in their environments, a cloud model in which droplets grow up by stochastic coalescence under the condition of srmultaneous fluctuation in water content and updraft is designed. According to the growth of precipitation particles by coalescence in clouds, a relationship between the droplet growth and its displacement in the cloud with cells is obtained and, we have also discussed the size distribution of precipitation particles after they have passed through the connective cells at random.