This study investigates the behavior of thick composite laminates using the high order method through hydrothermal stress calculation, the composite laminate is working in a hygrothermal environment, temperature and humidity are used and taken into account for stress calculation, different Simulations are carried out using different values of temperature and concentration, to see the influence of one on the other, other simulations are made by varying the distribution shape of temperature and humidity along the thickness of the laminate, the plate size is also taken into account in the simulations (a/b: ratio of length to width, a/h: ratio length to thickness).