Abstract: A diallel crossing design which contained seven parents of Cunninghamia lanceolata was carried out.From statistical analysis of general and special combining ability,effect in back and self crossing,and heterosis of five characters——height,breast-diameter,numbers of knot and branch,crown-diameterin four year's Cunninghamia lanceolata,the results obtained are as follows:(1) These five quantitative characters are mainly controlled by the effect of general combining ability; (2) There are also some effect of special combining ability and back crosses among the detinite parent's combinations; (3) Chinese Fir has considerable self-crossing rate but its failing effect is common,which we should pay attention to avoid or apply in the practice of breeding good strains and in the study on long term breeding; (4) It appears frequently the super-parent positive heterosis.These heterosis often related to general combining ability which could be acted as a standard of selecting parent when we make use of heterosis to breeding.