Abstract: The experiment was carried out to study the effects of combined application of organic fertilizers on the control of soilborne diseases and the regulation of soil microbial diversity in a tomato field by using the method of Biolog. The mechanism of soilborne disease control and its significance were also discussed. The results show that the combined application of organic fertilizers could control three kinds of the soilborne diseases, such as tomato Bacterial wilt（Ralstonia solanacearum）, Fusarium wilt（Fusarium oxysporum f. lycopersici）, and Basal stem rot wilt（Rhizoctonia solani）. The effect of combined application of the powdery organic fertilizer as base fertilizer and top-dressing liquid organic fertilizer at two times on control soilborne diseases is the best. The soil microbial community structure is improved with the application of organic manures. AWCD and Shannon index of soil microbial communities are greatly related to the incidence of the diseases. These results indicate that the organic fertilizer application could increase the soil microbial diversity, and has significant importance for controlling the soilborne diseases.