Abstract: The effects of liquid fertilizer drip irrigation and conventional fertilization on lettuce yield and active nitrogen losses (ammonia volatilization, nitrous oxide emission and nitrate leaching) were investigated. A field experiment was conducted in a greenhouse of lettuce, with three treatments of optimized fertilization mode with liquid fertilizer (LF, 170 kg N hm⁻², basal fertilizer without nitrogen + 3 topdressing), conventional fertilization mode with solid water-soluble fertilizer (CF, 200 kg N hm⁻², basal fertilizer + 2 topdressing) and no nitrogen fertilizer (CK, 0 kg N hm⁻², phosphorus and potassium as basal fertilizer + drip irrigation with clear water). Drip fertigation was adopted for topdressing and irrigation, and ammonia volatilization and nitrous oxide emissions were measured by the methods of aeration and static chamber, respectively. Compared with the CF treatment, the LF treatment could delay the emission peak of ammonia volatilization and nitrous oxide for 3-5 days in the early growth stage, and significantly reduced soil ammonia volatilization and nitrous oxide in the growing season by 24.6% and 21.6%, respectively. Also, it reduced soil residual NO₃-N by 21.0% at 0-100 cm soil depth. Additionally, it could not only save nitrogen input by 15.0%, but also achieve a high and steady yield and increase the nitrogen use efficiency by 32.4%. Generally, the LF treatment could significantly reduce ammonia volatilization and nitrous oxide emissions from greenhouse vegetable fields, alleviate the risk of soil nitrate leaching, and maintain the lettuce yield and improve the fertilizer utilization efficiency. Therefore, the application of new liquid fertilizer should be an effective measure to promote the efficient production of greenhouse vegetables.