Abstract: Previous experimental studies have shown that nonlinear factor in constitutive relations for composite materials in which epoxy works as mateix will increase significantly with inceasing temperature and moisture, which makes the analysis of bulckling problems for composites difficult and complex. In the case of high temperature and moisture environment,it may give rise to a notable error to consider composites as linear material,thus a nonlinear analysis becomes necessary for composites in hygrothermal environment. A lot of experimental work needs to be done for performing the nonlinear analysis because nonlinear effects of various temperature and moisture conditions as well as fiber volumes and orientations on composites have to be determined experimentally.