Delamination, a frequently observed failure mode in composite laminate, is a key issue in structural design and integrity prediction. In this paper, the stability of delamination crack is investigated for an angle-ply laminate subjected to uniform displacement and thermal loading. Due to the complexities of the problem, a quasi 3-dimensional finite element method is used to obtain strain energy release rate. The effect of parameters, such as temperature drop, loading type, stacking sequence, laminate thickness and width will be considered. Also, the effect of delamination crack on the tensile strength of angle ply laminate for small fiber orientations is evaluated by using a rule of mixtures and energy release rate concept in classical fracture mechanics.