Abstract: Through a large number of field measurements,time regulations of fruit expansion of the navel oranges Newherl,Roberson-35 and Pengla as well as internal relations among its growth characteristics are analysed.The results show that the expanding course of fruit obeys the regulation of Logistic equation.The relations among expanding rate,fruit diameter and expanding duration are consistent with those obtained from field measurements.Duration of fruit expansion is long,but with a small range,the variation of expanding rate is gentle.Among the three observed species,Newherl shows strong advantages in cultivation practice.Therefore,it should be popularized.