Abstract: In this paper, the soil microorganism quantitative distribution and its population of different age protective forest and species tree growing on argillaceos coast in Jiangsu Province were reported. The results showed that the mean microorganism biomass in the protective forest soil was more than 100 times greater coast soil, and more than 20 times greater cropland soil. As the microorganism consisted of bacteria, which was the chief content, actinomycete, and fungi which was the least present. In 1 gram dr.: soil, there were 9 to 80 million bacteri-a, 2 to 24 million actinomycete and 8 to 17 thousand fungi. The vertical distribution showed that the microorganism biomass was decreased when the soil depth was increased and they were mainly distributed in 0 to 20 cm depth of soil. As seasons changed, so did the microorganism, and more was present in spring than that in autumn.