Abstract: In this study,the effects of different dilutions on the growth and quality of lettuce were discussed by using the three kinds of nitrogen sources,such as amide nitrogen,plant amino acid powder and fish protein. The results showed that the fresh weight,chlorophyll,reducing sugar and protein content of lettuce were increased by 23.21%,4.21%,35.48% and 35.71%,respectively,compared with the modified hoagland formula when the dilution ratio of amino acid powder seaweed was 3000 times,and the nitrate content reduced by 60.31%. When the dilution ratio of fish protein seaweed fertilizer was 2000 times,the contents of fresh weight,chlorophyll,reducing sugar and protein were increased by 21.94%,14.81%,15.21% and 24.85% respectively,and the content of nitrate decreased by 57.96%. When the the dilution ratio of amide nitrogen(urea)seaweed fertilizer was 1800 times,the fresh weight,reducing sugar and protein content of lettuce were increased by 15.25%,16.31% and 8.33% respectively,and the contents of nitrate and chlorophyll decreased by 2.10% and 15.09% respectively. The results showed that amino acid powder seaweed fertilizer was the most suitable for lettuce cultivation of organic fertilizer.