Abstract: Cones were harvested from 20-30-year Pinus thunbergii at coastal protection forest in Yantai of Shandong province in September of 2016. The seeds were divided into large, medium and small size and sown in pots covered with different litter thickness (1, 2, 3 and 4 cm). The results showed that seed size had significant effect on germination rate and germination index, but no significant effect on average germination time and vigor index. Large seeds had lower germination rate and index than medium and small ones. Seed size had no significant effect on biomass allocation and root growth, but had significant positive effect on height and ground diameter growth of seedlings. Germination rate, germination index and vigor index had positive relation with litter thickness, while the average germination time had negative one. Litter thickness had no great effect on seedling biomass, biomass allocation and root growth. Correlation analysis showed that seedling height and ground diameter had no significant relation with germination index and seedling biomass allocation, but had evident positive relation with specific root length and specific root area.