Abstract: Effects of inoculation of ectomycorrhizal fungi on the seedling growth of Castanopsis fissa were studied in this paper. The results showed that mycorrhizal fungi agent could effectively increase the infection rate of C. fissa mycorrhizal. The best treatment was to dispose each seedling with 10mL dry mycorrhizal agent in the planting pit. The second good treatment was blending 1L mycorrhizal agent with 2.5 kg water and yellow mud evenly for seedling dipping prior to the transplantation. It was observed that the mycorrhizal infestation of Castanopsis fissa seedlings could happen naturally though the infestation rate varied greatly. The maximum infestation rate was 406%, and the lowest was 2.0%, the difference was about 20 times.