Abstract: 【Objective】 This research aims to study the effects of 'Jun Lin Tian Xia' microbial inoculant on cotton growth and development, yield and quality traits and soil physico-chemical properties. 【Methods】 The field demonstration method was adopted: 133.33 hm² of microbial agent demonstration and 133.33 hm² of control (7th company, 149 th regiment: 53.33 hm², 11 th company, 134 th regiment: 40 hm², 13 th company, 141th regiment: 40 hm²). The agronomic traits were investigated at seedling stage, bud stage and flowering and boll stage, and the yield and quality traits were measured at boll stage. 【Results】 Cotton boll opening could be 2 d earlier than the control. The number of bolls per plant increased by 0.11-0.3, the number of bolls harvested per mu increased by 12,090-18,708, and the single boll weight increased by 0.03-0.3 g ; the yield of seed cotton was increased by 76.0-100.46 kg/667m² per mu compared with the control, and the yield of seed cotton was increased by 47.66-66 kg/667m². The lint percentage increased by 0.57-1.14 percentage points, the breaking strength was 0.4-0.8 percentage points, and the Micronaire value decreased by 0.2. At the same time, the use of microbial agents could reduce and improve soil structure, activate soil phosphorus, and increase soil available phosphorus content. 【Conclusion】 The application of microbial inoculants can promote the growth and development of cotton, increase yield and improve quality. At the same time, the use of microbial inoculants can reduce and improve soil structure, activate soil phosphorus and increase soil available phosphorus content.