Abstract: Based on the two-dimensional elasticity theory, the buckling of delaminated composite beams is investigated by means of the point collocation method. Firstly, according to the plane elasticity theory, the analytical solution of a piece of homogeneous beam is obtained, which satisfies the simply-supported conditions of the beam at both ends. Then, using the point collocation technique, the laminated beam is divided into equidistance along the interface of the beam. Taking the series numbers to be equal to the matching points, the buckling loads are obtained by means of the interface equations at every points as well as the upper and lower surface conditions of the beam. The numerical results show excellent convergence with high accuracy. The effects of delamination positions and delamination sizes on the critical buckling loads are investigated in details. The proposed solutions are compared with those from the classic beam theory based on plane section assumption, which is only valid for the slender beams. However, the proposed method is applicable to both slender beams and thick beams.