Population dynamics of American serpentine leafminer, Liriomyza trifolii, were modeled and simulated to compare the temperature effects of air and tomato leaf inside greenhouse using DYMEX model simulator. The DYMEX model simulator consisted of series of modules with the parameters of temperature dependent development and oviposition model of L. trifolii from pre-published data. Leaf surface temperature of cherry tomato leafs was monitored according to three tomato plant positions using an infrared temperature gun. Air temperature was monitored at same three positions using a self-contained temperature logger. Data sets of observed air temperature and average leaf surface temperatures were prepared, and incorporated into DYMEX simulator to compare the effects of air and leaf surface temperature on population dynamics of L. trifolii. The number of L. trifolii larvae was counted by visual inspection in tomato plants to verify the performance of DYMEX simulation. The egg, pupa, and adult stage of L. trifolii were not counted due to its availability of visual inspection. Based on correlation analysis, L. trifolii was affected greatly by the leaf temperatures, rather than air temperatures.