The amount of nitrogen fertilizer is an effective factor on the growth، development، and reproduction of phytophagous insects. To investigate the effect of nitrogen fertilization on intrinsic rate of increase of cabbage aphid، Brevicoryne brassicae L.، plants rape oilseed (RGS003cultivar) were treated with four nitrogen levels (zero (check) 50، 100، and 150% of recommended levels. The results showed that increase in nitrogen fertilization resulted in increase in the percentage of soluble nitrogen concentration in plants. All the experiments were carried out at environmental chamber (25±1ºC، 70±10% RH، and 14:10 L: D photoperiod). The aphids feeding on plants receiving higher nitrogen fertilizer (150%) had shorter pre-reproduction period، longer reproductive، as well as greater fecundity، although nitrogen fertilization had no effect on adult longevity. The intrinsic rate of increase in four treatments was determined as 0. 249، 0. 215، 0. 267، and 0. 317 (female/female/day)، respectively. The results revealed that cabbage aphid developed on treated plant with 150% nitrogen had the highest population growth. This means that higher nitrogen fertilization improves the susceptibility of rape oilseed for cabbage aphid.