The fertility occupies a central position in the study of population growth.The growth of the population depends entirely on human fertility,including birth,death rates and life expectancy.Growth of the fertility is one of the key determinants of the Population Growth.This paper focused on the determinant factors of population growth in Rwanda.From the findings,there is a statistically significance of fertility trends at 0.05 percent because the t-statistic in table-4 is greater than its critical value(1.96)at 0.05 percent.The results provides evidence of Fertility,birth,death and life expectancy as factors which boost population to grow in Rwanda.The results founded,indicate the existence of high fertility rates even decreasing,lead to increase population due to its positive values over time.This means that Fertility rates in Rwanda has a positive impact on the country's population growth,especially in the youth who realizes around 48 percent of entire Rwandan’s Population.The relationship between fertility rate and the time describe a decreasing function,which interesting for us showing that fertility has been reduced over time.In other words,as well as the years increased,the fertility decreased.The coefficient of Time is(-0.117035)which implies that a unit change in time will change Total Fertility Rate(TFR)by(-0.117035),table-1.The model of fertility represents a decreasing function while the time function still increasing,as shows in the figure-2.The fertility variable has positive relationships with the population dependent variable even the fertility coefficient is negative,the probability p-value is significant at 0.05 significance level on one hand and the absolute t-statistic is great than the critical value at 0.05 level of significance,which confirm the statistically significance of t-statistic.The coefficients on the death rate and Life expectancy are respectively positive and significant at all confidence level,table-5.