The effects of different nitrogen treatments(5 mmol·L NO-3-N,10 mmol·L-1 NO-3-N,5 mmol·L-1 NO-3-N+5 mmol·L-1 NH+4-N)on the growth and physiological characteristics of Lactuca sativa L.var.ramosa Hort were studied.The results showed that after 35 days,NH4 + -N inhibited the growth of lettuce with the same nitrogen concentration.The leaf area,plant height,aboveground fresh weight,aboveground dry weight,underground fresh weight and underground dry weight decreased by 78.2%,60.4%,87.0% ,81.3%,80.1% and 87.5% respectively(P<0.05).In addition,there were significant differences in their physiological activities such as root activity,soluble protein,superoxide dismutase activity and nitrate reductase activity(P<0.05).Compared with the treatment of 10 mmol·L-1 NO-3-N(12.89 g),the biomass of lettuce reduced slightly with the treatment of 5 mmol·L-1 NO-3-N(8.90 g),and the leaf area,root length and underground dry weight decreased by 48.1 %,50.3% and 37.5% respectively(P < 0.05),but the content of soluble sugar and anthocyanin increased by 67.5% and 51.9% respectively(P<0.05),while the ratio of NO-3-N uptake reached the maximum on the 21st day,which was 3.15 times of the former.Our results showed that the creamy lettuce was a nitrate favorite vegetable,and the optimum concentration of nitrate nitrogen in lettuce was high(10 mmol·L-1)in early prophase(21 days)in order to promote the growth of butter lettuce,but later(21 days)low concentration(5 mmol·L-1)was better to improve quality.