In order to study the law of growth and development of fly maggot, the body mass data of 1.0-4.0 day old fly maggots were collected every 12 hours with total 7 time sampling points. The growth curves of 7 points were fitted by Gompertz, Logistic, Bertalanffy nonlinear growth models. The results showed that all the three nonlinear growth models had high fitting degree(R2>0.970), among which the Bertalanffy model had the best fitting effect(R2=0.988), but its inflection point was far from the actual measured value. Logistic model the inflection points fitted with the Gompertz model were (1.75 d, 13.64 mg), (1.53 d, 10.30 mg), which could better reflect the growth law of fly maggot body weight, but the fitting degree of Logistic model(R2=0.978) was smaller than that of Gompertz model(R2=0.986), and the overall standard error was large. It can be seen that the Gompertz model was most suitable to fit the growth and development law of fly maggot body mass.