To optimize cultivation method for high-quality rapeseed blanket seedling and to improve seedlingraising system, Brassica napus cultivar Ningza 1838 (double-low variety) was nursed in traditional rice seedling trays for rapeseed blanket seedling. Mixture of ammonium sulfate in substrate with different amounts was used to an⁃alyze regulation effect of ammonium sulfate on the seedlings. Agronomic characteristics and dry organ weight weremeasured for seedlings from different growth period. Results showed that optimum dosage range of ammonium sul⁃fate was 4.37-4.62 g per plate. Under the dosage, survival plant numbers, leaf numbers, spread leaves and greenleaf area were significantly increased. Dry matter accumulation was increased most, which was the most conduciveto the recovery of green seedlings after transplanting from the blanket seedlings.