Cooperative transportation has become popular in recent years due to the development of multi-robot system. The whole transportation task is composed of several subtasks like formation control, team navigation, and dynamic obstacle avoidance. In this paper, we mainly focus on optimization-based control for cooperative transportation task. First, we describe the second-order dynamic of multi-robot system, and then define constraints for each subtask to establish the form of optimization problem. Second, we propose a controller based on hierarchical quadratic programming method to cooperate subtasks with different priorities. Finally, we design simulations to validate the effectiveness of our controller.