Development of mycorrhizal infections were estimated by assesing the percentage of VAM infection in growth intervals of mungbean in pot cultures with fluvo-aquic soils of Huang-Huai-Hai plain and red soils derived from quaternary red clay, granite and basalt in Jiangxi and Guangdon provinces, most of which were deficient in available phosphorus. Results showed that infections of indigenous VAM fungi in most soils were low and lag phase usually presented. In most of the fluvo-aquic soils, VA mycorrhizal infections were around 10% on the 20 days seedlings. After inoculation, infections of both mungbean and white clover in sandy and loamy fluvo-aquic soil increased to 20-30% during the early stage of seedlings.In red soils derived from quaternary red clay in Jiangxi province, VAM infection was 13% on 40 days seedlings, it increased up to 50-60% during 25-40 days by inoculation. In red soils derived from other parent materials in Guangdon province had the same tendency with those in other districts. Lag phase of infections were all decreased or even disappeared by introducing mycorrhizal fungi into the soil, and plant growth was greatly promoted.