The present study was conducted to survey and population density of aphid Aphis gossypii Glover (Homoptera: Aphididae)  infesting cucumber plants and its parasitoids were investigated at Diarb Nigem district during two season 2015 and 2016. Three primary parasitoids Lysiphlebus fabarum (Marshall), Diaeretiella rapae (M Intosh) and Binodoxys angelica (Haliday) and a hyperparasitoid, Pachyneuron sp. ((Hymenoptera: Aphidiidae)), were recorded. Primary parasitoid Lysiphlebus fabarum was the highly dominant species by relative density 53.76 and 52.24%, followed by D. rapae 22.58 and 27.73%, Binodoxys angelica 15.06 and 12.14%, while the hyperparasitoid , Pachyneuron sp., occurred by 8.60 and 7.89%, during 2015 and 2016 seasons respectively. The percentage of parasitism ranged from 3.14 % to 21.0 % in 2015, while it is starting by 2.66 % to reach its maximum 42.66% in 2016. Total developmental period of the parasitoid Lysiphlebus fabarum was 14.67 ± 1.16 days at 18.30°C ±1°C and 64 ±2RH%. Investigation the behaviour of the same parasitoid Lysiphlebus fabarum at varying   host densities showed increase number of sting and number of mummies increased with increase of host density but decrease leaf arrival times and host arrival times with increasing . The obtained results showed that the longevity of the parasitoid Lysiphlebus fabarum was affected by temperatureand food supply.