The aimed of this study was to investigate some biological aspects of cotton mealybug (CM), Phenacoccus solenopsis Tinsley, found on potato in Sharqiya Governorate, Egypt. The results showed that there are three nymphal stages in females. Adult males have two nymphal and pupal stages, they are winged, delicate and do not feed. The development period for the first, second and third nymphal instas for insect female were 6.20, 4.26 and 4.46 days. While, in the male nympal stage, the first, second in stars were 6.90 and 7.00 days, respectively. The ovipostional periods were 15.08, 15.98 and 4.36 days were recorded for the pre-oviposition, oviposition period and post ovipostion period, respectively. The adult longevity for female and male presented by 35.4 and 2.2 days, respectively. The generation period and the life cycle for the insect females recorded 30.52 and 86.34 days, respectively. Female fecundity shows a dynamic pattern with the number of female-producing reptiles varying between 122 and 459, with an average of 335±11.00 /female.