The larval cuticle layer of Aldrichina grahami was studied under constant temperatures 15℃,20℃,25℃ and 30℃. The results showed that (1) The largest number of cuticle layers for the first instar larva was eight, the second eleven, but the third variable depending on temperature, for 15℃, 20℃,25℃ and 30℃ the numbers were sixty-nine, seventy-seven, ninety-two and eighty-one.(2) New secreted layer was thicker than the old one, the average thickness of the layer increased as the developing time, after getting the largest thickness the layer got thinner as the time elapsed. (3) Depositive rates of the layer at different constant temperatures were variable. There was not a linear relationship between the depositive rate of the layer and the developing time. It is a useful way to estimate insect daily age by the larval cuticle chitin layers changing, and this can be used in forensic entomology through establishing suitable mathematic model by further study.