The characteristics of old natural forest of Castanopsis tibetana in Liangyeshan National Nature Reserve of Fujian Province were studied by phytocoenology investigation in the method of temporary sample strip plot. The results showed that the stand was composed of 21 tree species in tree layer. The stand dominant species was Castanopsis tibetana of which important value and growing stock in whole stand were 36.2% and 71.4% respectively. The species richness (R),Shannon-Wiener index (SW),evenness (E) and ecological dominance (ED) in tree layer were 21,3.70,0.50 and 0.105 respectively,and they were 4,1.11,0.20 and 0.571 respectively in tree sub-layerⅠ,and 21,3.91,0.56 and 0.041 respectively in tree sub-layerⅡ. The species richness (R),Shannon-Wiener index (SW),evenness (E) and ecological dominance (ED) in shrub layer were 44,4.63,0.61 and 0.060 respectively. The stand average DBH,height,density and growing stock were 29.6 cm,15.7 m,790 N/hm ² and 395.5 m³/hm² respectively,and they were 50.0 cm,18.1 m,214 N/hm² and 329.4 m³/hm² respectively in tree sub-layerⅠ,and 16.4 cm,11.4 m,576 N/hm² and 66.1 m³/hm² respectively in tree sub-layerⅡ.