Experiments were carried out in the orchards farm of the Fac. of Agriculture at Moshtohor, Benha University, Egypt on navel orange (Citrus sinesnes)seedlings grafted on Citrus volckamerianatostudy the effect of releasing 2^nd instar larvae ofthe aphid lion (Chrysoperla carnea) on citrus leaf miner (Phyllocnistis citrella) infestation rate in nursery of citrus plants.The efficiency of Ch. carnea as a bio-agent against the citrus leaf-miner was estimated.A net wooden cage was divided into 12 cages that measured 75×75×250 cm. each, and covered tightly with screenedfine nylon from all sides. Three treatments were examined compared with control (Tr.1: one & Tr.2: two and Tr.3: four 2^ndinstar larvae of Ch. carnea/ seedling). Obtained data clarified that releasing Ch. carnea on citrus seedlings caused considerable reduction in both the whole mean number of infested leaves and whole mean percentage of infestation by P. citrella. Treatment 2 was the best in reducing the seasonal mean infestation rate by P. citrella in citrus nursery by 43.70%while, the treatment 3 gave the best results in decreasing the numbers of P. citrella mines, larvae, pupae and infested leaves by 50.86, 78.37, 72.47 and 52.68 %, respectively. The mentioned treatments caused reductions in the whole mean number of mines, larvae and pupae of P. citrellato be 7.14, 1.14 and 0.68/seedling, respectively.