Abstract: Regression between litter size and parity in fat-tailed sheep was analyzed using SPSS software. The quadratic regression and cubic regression goodness of fit （R2） of litter size and parity was high in fat-tailed sheep, 0.924 6 and 0.926 9, respectively. All regression parameters of quadratic regression equation between litter size and parity reached highly significant level （P〈0.01）, which showed the quadratic regression equation between litter size and parity has a certain application value.