Abstract: The experiment of seedling density of Cunninghamia konishii was carried out with annual seedlings. The effects of seedling density on seedling growth dynamics, comprehensive performance and growth rhythm were analyzed by using the method of fixed plant observation and fitting seedling growth dynamics with Logistic equation. The results showed that the effects of seedling density on seedlings height, ground diameter growth appeared with the time after treatment, and it is a dynamic process. The effect of seedling density on seedling height and ground diameter of C. konishii is different. High seedling density had promoting effect on seedling height, but restraining effect on ground diameter. Seedling density significantly affected the seedlings height and ground diameter, the yield of first grade seedlings, qualified seedlings, and seedling comprehensive performance, the comprehensive performance appeared first increased and then decreased with the increase of seedling density. Logistic equation fitted well the growth of height and ground diameter of C. konishii seedling. Seedling density significantly affected the height and ground diameter growth rhythms of C. konishii seedlings, such as the linear beginning days, linear final days, linear growth duration, linear growth rate, maximum linear growth rate and total linear growth. High seedling density reduced seedling height and ground diameter linear growth final days, and shortened linear growth duration. Low seedling density significantly reduced total linear growth, linear growth rate and the maximum linear growth rate of seedling height, but significantly increased total linear growth of ground diameter. The CK significantly reduced total linear growth, linear growth rate and the maximum linear growth rate of ground diameter. It is important to adjust the nutrient supply of fast-growing stage according to the different seedling densities.