Abstract: The butter head lettuce was used as experimental material, the growth and quality of lettuce were determined by using different concentrations of exogenous DL-selenomethionine, in order to provide reference for the research and application of vegetable selenium-enriched production.The results showed that root irrigation with exogenous DL-selenomethionine had significant increase the high, plant-spoke, number of leaves, leave area, fresh weight and dry weight of aboveground and underground lettuce, and increased the content of total chlorophyll, soluble sugar, soluble protein, vitamin C and selenium, decreased the content of nitrate nitrogen.The effect of low concentration on the physiological indexes of lettuce was not obvious, and the high concentration of exogenous DL-selenomethionine treatments made the selenium content of lettuce exceed the national standard, which was not suitable for production.In conclusion, the DL-selenomethionine treatments of lettuce with a concentration of 1.0 mg·L^-1 had better effect on quality improvement and yield increase.