The tree stratum of 19 year-old semi-natural forest of Cunninghamia lanceolata and broad-leaved trees was stratified obviously to 2 sub-strata (sub-stratum I and sub-stratum II) by MLRP (Maximum Light Receiving Plane) method.The tree height in sub-stratum I was higher than or equal to 13.0 m.Its average stand DBH,height,density and growing stock in tree stratum were 13.7 cm,14.6 m,2 867 N/hm² and 309.7 m³/hm² respectively.Its average stand DBH in sub-stratum I and sub-stratum II were 17.1cm and 10.3 cm respectively.Its average stand height in sub-stratum I and sub-stratum II were 16.4 m and 10.6 m respectively.Its percentage of stand density in sub-stratum I and sub-stratum II were 43.60% and 56.40% respectively.Its percentage of growing stock in sub-stratum I and sub-stratum II were 74.98% and 25.02% respectively.There were 17 tree species in tree stratum and C.lanceolata was the absolutely dominant tree species,with the important value of 61.88%.There were 8 and 17 tree species in sub-stratum I and sub-stratum II respectively.The important value of C.lanceolata (the absolutely dominant tree species) in sub-stratum I and sub-stratum II was 76.20% and 58.31% respectively.Its species richness (R),Shannon-Wiener index (SW),evenness (E) and ecological dominance (ED) in tree stratum were 17,1.46,0.36 and 0.62 respectively,which in sub-stratum I was 8,0.83,0.28 and 0.78 respectively.And the value in sub-stratum II were 17,1.80,0.44 and 0.51 respectively.