Economic injury levels and economic thresholds were estimated for the american serpentine leafminer (Liriomyza trifolii) on greenhouse eggplant. Liriomyza trifolii density was increased until the late June and decreased after the July in innoculation on may 17. Growth of an aerial plants and fruits were not different in treatment respectively. But total number of fruits and yields were decreased on higher inoculation density. Whereas the rate of yield loss was increased. The rates of damaged leaf by L. trifolii were increased on higher inoculation density and the peak was 65%. The number of commodity fruits and the rates of commodity fruit were become lower than non-treatment (72.2%). The rates of damaged leaf area were 5.3, 11.7, 19.7, 25.7% on inoculation densities and the rates of yield loss were 0.6, 4.8, 9.8, 14.7%, respectively. There existed close correlation between rate of yield loss and inoculation density (Y = 0.76779X + 0.298354, R² = 0.9599). Considerated of the results, the economic injury levels of L. trifolii on eggplant greenhouse was 6.1 adults per 4 plant and the economic thresholds was 4.9 adults per 4 plant