This research aimed to study the differentiation of soil microorganisms in vegetable fields of organic, GAP and chemical crop productions system in Mueang Nakhon Pathom, Kamphaeng Saen and Don Tum District, Nakhon Pathom Province. The questionnaire was collected an information from farmers and random sampling of soil, 2 plots/system, 2 times each, 4 weeks apart.  The soil type was observed and measured the pH value. The results found that most of the soil types were loam and some were clay and sandy soils, and the pH of the soil in each production system was from 6.5-7, 6.5-7 and 5.5-6.0, respectively. The results of the study of total soil microorganisms, free nitrogen fixing bacteria content and the total amount of yeast and mold (cfu/g) were found that the soil from the organic vegetable plots found the highest 3 groups of microorganisms. Next up is the GAP and chemical crop productions system, respectively.