Abstract: To investigate the effects of the different nitrogen and phosphorus supplying levels on development of arbuscular mycorrhizal fungi (AMF), a pot experiment was conducted with cucumber (Cucumis sativus) and tomato (Lycopersicon esculentum) as the host plants, and the semi-hydroponic system was used to cultivate the crops with different N, P concentrations based on LAN solution. The results show that there are not any significant differences of biomass between mycorrhizal and non-mycorrhizal cucumber under the same N and P treatments. AMF development is significantly affected by the N and P treatments. The more the nitrogen application, the more the AMF structure, the lower the shoot phosphorus concentration for the two plants. The influences of phosphorus application vary with the nitrogen application rates, when N content in the nutrient solution is about 0.3 mmol/L, AMF structure is decreased with the increase of P content, while when N contents in the solution are larger than 3 mmol/L, AMF structure is increased with the increase of P content. It is presumed that the effects of nitrogen on AMF structure are not direct and may be derived from interaction of nitrogen and phosphorus based on which effect on AMF structure and phosphorus nutrient status.