Abstract: During the early days (5～10 days after germination ), blue light promoted the accumulation of soluble protein . Seedlings treated by blue light for 5 days had far more contents of soluble protein, total_N,protein_N, nonprotein_N, Asp,Asn,Glu,Gln than those in seedlings under white or red light. With the seedling_age goes on, the promotion of blue light becomes weaker. 17_day_old seedlings treated by blue light had less content of protein or free amino acids. Compared with blue or white light, red light is less effective to stimulate the accumulation of protein, and after 10 days, the contens of Asn and Gln are more than those in seedlings treated by blue or white light.