Abstract: During 2019-2020, 29 islands dominated by Pinus massoniana with few human disturbance were selected in the Thousand Island Lake, Chun’an, Zhejiang province to establish forest dynamic plot. In spring of 2011, 498 quadrats were built in the 29 islands for investigation of seedlings in spring and autumn from 2011 to 2015. Results showed that there was a trade-off between seed mass and seed number. Seed mass had no significant effect on seedling survival rate within half a year. The aspect and the lack of soil carbon content had positive effect of seed mass on seedling survival rate. Larger mass had greater negative effect than small mass on seedling survival rate in summer. Seedling initial height and soil phosphorus content showed positive effect on seedling survival rate, while distance to the nearest island had negative effect on seedling survival.