Abstract: CLB111,KW214 strain(belong to Rhizoctonia sp.) and CLB113 strain belong tc Orchidaceous rhizotonias)were inoculated to tissue culture seedlings of Cymbidium goeringii. After 4.5 months of inoculation, the growth of seedlings was promoted at different level, The average fresh weight of seedlings treated with CLB111, KW214, CLBll3 strain were 170.6%,170.2%//o and 166.1% respectively that of their initial value, while that of the control is just 145.6%. The statistic showed that fresh weight of the seedlings inoculated with strain CLBl11, CLB113 were extremely significantly higher(a:0.01), while fresh weight ot seedling inoculated with KW214 was significant higher than that of control (α ＝0.05). The observation under optical and electronic microscope for CLB111, CLBl13and KW214 found the pathway of infection and structure of mycorrhizal in C. goeringii. For the C. goeringii, mycorrhizal structure was same with the general nutrition roots of control structure. The infection pathway was that fungi invaded velamen firstly, then entered cortical tissue by breaking the velamen and the colonized and infected other cells continuously by means of hyphae penetrating the cell wall. There was a lot of pelotons which appeared in dark colour and in