Abstract. In various scientific experiments, experimenter always get some discrete data, to estimate the function with the original rules from these data, interpolation is a method for dealing with this kind of problem.But when the discrete data is too much,it can be caused serious distortion which is called Runge phenomenon at the interval endpoints.To avoid,the Curve Fitting Least Square method is a kind of optimal solution. The Curve Fitting Least Square method is used to be dealing with structure prediction model etc.In this paper, Malthusian model is the method of population predicting.In Malthusian model,the unknown variable is ascertained by the Curve Fitting Least Square method.