Abstract: The occurrences of rice false smut under three nitrogen levels (N1, N2, N3) combined with four seedling-throwing densities (M1, M2, M3, M4) were compared to investigate the occurrence regularity of rice false smut under nitrogen- reduction and seedlings- increase condtions. The results showed that: every incidence parameter presented a decreasing trend with increased densities under the same nitrogen level, while an increasing trend with increased nitrogen level under the same density. Three incidence parameters of the combination of N3M1 reached the highest level in comparing with other combinations, and the rate of diseased grains, diseased panicles and diseased plants was 0.89%, 21.69% and 95.88%, respectively. The correlation coefficients R2 between SPAD value and the rate of diseased grains, diseased panicles and diseased plants were 0.668, 0.8472, 0.9441, respectively, which reached significant or extremely significant level. The correlation coefficients R2 between leaf area per plant and the rate of diseased grains, diseased panicles and diseased plants were 0.9143, 0.9427, 0.984, respectively, and all reached extremely significant level. In summary, reducing the supply of nitrogen and increasing planting density properly would be beneficial to esta population structure of late rice reasonably and reduce the occurrence degree of rice false smut effectively.