Global climate changes have become hot topics in ecological research filed in last decade. Picea asperata, the constructive species of the Southwest subalpine coniferous forest which is well known for its sensitivity to climate changes in China, is a typical ectomycorrhizal species. Ectomycorrhizal fungi play an important role in the forest system by enhancing the ability of host trees which form ectomycorrhizal symbionts with them to uptake nutrient and water, promoting seedling establishment and improving nutrient cycling in the forest by the mycorrhizal networks belowground. Many scientists have already studied the effects of warming and nitrogen deposition on Picea asperata's physiology and phenological phenomenon. But how ectomycorrhizal symbionts and ectomycorrhizal fungal community associated with Picea asperata respond to warming and nitrogen deposition in this area is lack of research. To simulate the effects of warming and nitrogen deposition, we conducted an experiment with the infrared radiator and NH₄NO₃ 25 g N m^-2 a^-1 fertilizing. And we evaluated the effects of 3-year continuous night-time warming and nitrogen fertilization on the ectomycorrhizal colonization rate of Picea asperata seedlings, soil ectomycorrhizal fungal biomass and the diversity of soil ectomycorrhizal fungal community. The experimental results clearly showed that the effects of night-time warming on the ectomycorrhizal colonization rate were varied seasonally in different root orders. In spring (May, 2011) night-time warming significantly affected the ectomycorrhizal colonization of first-order roots, however, in summer (July, 2011) and autumn (Oct, 2010) the ectomycorrhizal colonization rate of second-order roots were changed significantly. Nitrogen fertilization didn't dramatically affect the ectomycorrhizal colonization rate of first-order and second-order roots except for the colonization rate of first-order roots in July 2011. There were no significant effects of night-time warming on soil ectomycorrhizal fungal biomass and the diversity of ectomycorrhizal fungal community. But we found that nitrogen fertilization and the interaction of the two treatments affected them significantly: the soil ectomycorrhizal fungal biomass was decreased while the diversity of ectomycorrhizal fungal community was increased. These results indicated that the ectomycorrhizal colonization rate of Picea asperata seedlings was sensitive to warming, however, the soil ectomycorrhizal fungal biomass and the diversity of ectomycorrhizal fungal community was sensitive to nitrogen fertilization. The primary effect of night-time warming was to increase the ectomycorrhizal colonization rate, but there was negligible or insignificant effect on diversity of soil ectomycorrhizal fungal community. On the contrary, nitrogen fertilization directly and significantly affected the diversity of soil ectomycorrhizal fungal community rather than the ectomycorrhizal colonization rate of Picea asperata seedlings. The different response of different ectomycorrhizal fungus to the global climate change and long-term experiments simulated natural climate change will be considered in the following studies. The findings of our research provide the scientific basis for further studying the response mechanism of below-ground of southwest subalpine coniferous forest to global climate changes in this region.