Abstract: 【Objective】 Microsclerotia of Verticillium dahliae in soil is the basis of cotton Verticillium wilt. This project aims to clarify the influence of external factors on microsclerotia in soil and provide a solution for the prevention and control of the disease. 【Method】 The microsclerotia in soils collected from cotton field with Verticillium wilt under different treatments were detected using selective isolation and culture technology, and verified by indoor pot experiment. 【Result】 Microsclerotia were aggregated in the soil of cotton field. Its number in the cotton rhizosphere was not significantly correlated with its disease resistance. Comparing cotton with upland rice, at the flowering and boll-forming stages, the number of microsclerotia in the cotton rhizosphere was significantly higher than that in the rice rhizosphere. At the harvest stage, the number of microsclerotia in the rice rhizosphere increased significantly, but showed no significant difference with the number of microsclerotia in the cotton rhizosphere. Indoor pot experiment revealed no significant differences in the number of microsclerotia in the rhizosphere soil between disease-resistant varieties Zhongzhimian 2, Zhongzhimian 2 + rice treatment and susceptible variety Junmian 1, Junmian 1 + rice mixed treatment. Water flooding was performed for the soil. After 20-30 days of waterflooding, the number of microsclerotia in soil increased significantly, but decreased slightly at the 60th day. After 150 days, the number of microsclerotia increased to the highest level, which was five times as much as that in the initial stage. The dynamics of growth and decline of microsclerotia in soil under rice + waterflooding treatment were consistent with those in blank control, presenting a trend of rapid increase, then decrease and then increase. The number of microsclerotia at the 150th day was 8 times as much as that in the initial stage. 【Conclusion】 Microsclerotia are aggregated in the soil of cotton field. The number of microsclerotia in the cotton rhizosphere is not significantly correlated with its disease resistance. Planting upland rice in field can delay the growth of microsclerotia in early stage. Water flooding significantly promotes the growth of microsclerotia in potted planting soil. Rice planting fails to inhibit or even fail to promote the growth of microsclerotia in soil.