Cotton aphid, Aphis gossypii (Glover) is one of the most important pests of vegetables and ornamental plants in fields and greenhouses conditions; thus, it is highly important to be controlled. In this study, to estimate the Proteus (OD 11%) LC10, LC20 and LC30 concentrations, bioassays were performed by leaf-spraying method. The calculated values were 25.488, 44.382 and 66.205 ppm and confidence limits (18.0 - 33.4), (33.9 -55.1) and (53.1-79.7), respectively. Then the sub-lethal effects of mentioned concentrations and control (distilled water) were studied on biological parameters of the pest. For each treatment, 130 tritonymphs were placed in two Petri dishes and concentrations were sprayed on them at a distance of 20 cm. Then, after 24 hours, 100 individuals were randomly selected and placed in separate Petri dishes in laboratory conditions with 25 ± 2 °C, of 65 ± 5 % RH and a photoperiod of 16L: 8D. After three days, 80 protonymphs were randomly selected among the original 100 individuals as the second generation and kept in separate Petri dishes. The number of offspring produced by each female per day was recorded until the death of the last individual for both generations. Data was analyzed by using SAS software for the first generation and was performed according to the Age-Stage Two Sex Life Table theory for the second generation. According to the results obtained, total fecundity rate and longevity of cotton aphid was affected by different treatments and by increasing the concentration used, total fecundity and longevity of the pest decreased. Total fecundity rate in the control, LC10, LC20 and LC30 were recorded as 80.24, 58.47, 41.23 and 25.88 nymphs respectively. Daily reproduction in the control, LC10, LC20, and LC30 treatments was recorded as 13.18, 11.60, 7.53 and 6.68 (nymphs/day) respectively. Population growth parameters including the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) showed a decrease compared to the control. The intrinsic rates of increase in the control, LC10, LC20 and LC30 was calculated to be 0.48, 0.31, 0.25 and 0.17 (day-1), respectively. Furthermore, the value of the finite rate of increase varied from 1.18 (day-1) in LC30 treatment to 1.62 (day-1) in control. The net reproductive rate in the cotton aphid decreased from 78.64 in the control to 17.6 (offspring) in LC30. The recorded values for mean generation time (T) also varied from 9.04 day in control treatment to 17.17 day in LC30 treatment. The results obtained in this study can used in integrated management programs of cotton aphid in order to reduce the negative effects of pesticide on non-target organisms.