Abstract: The purpose of the present research is to study the effect of different photoperiodism; long (18L: 6D), medium (12L: 12D) and short (6D: 18L) as well as three levels of food (high, medium and low level) on the population density of albino mice (MFI). At medium food level, the onset of pregnancy delayed with decreasing photoperiodism and was proved statistically, r = -1.000 (p = 0.000) for the first and second generations of offsprings. There is an insignificant direct relationship between photoperiod and mortality rate (r = 0.997) for the first generation and no relationship between them for the second generation (r = 0.0). The surviving of population depends on the amount of available food whatever the photoperiod was long or short. It is obvious that when the females supplied with high level of food and exposed to long photoperiod is the best environmental condition for the earlier pregnancy onset (five weeks), larger numbers of neonates larger (42 individuals) and lower mortality rate (7.80%). Short photoperiod and low food level are considered as the bad condition and delayed the pregnancy onset (ten weeks), decreased the number of neonates (30 individuals) and increased mortality rate (93.4%).