Abstract: A unified procedure for optimizing of laminate stacking sequence of composite cylindrical shells subjected to linear buckling in order to bear maximum critical load is presented. This approach is based on the using of Binary Ant Colony Optimization (BACO) Algorithm and Finite Element Method (FEM). The optimization parameter is fiber angle which will be selected from a finite set of angels. On one hand, BACO is used for optimization process integrating and on the other hand, FEM is applied for calculating critical buckling load. For flexibility of algorithm, the pheromone release on nodes instead of edges is utilized to avoid modeling this problem in the format of Knapsack one. Knapsack problem which has the most similarities with composite stacking sequence is considered for algorithm evaluation. Results have shown that BACO in comparison with other optimization algorithms like genetic and particle swarm, has found the optimal solution in less function evaluations.