This paper presents a constructive design of a formation controller for leader-follower quadrotors in cluttered environment. To avoid collision in the formation and with obstacles, a path planning and collision avoidance function based on visibility graph, Dijkstra algorithm and smooth step function are embedded in the controller. An attitude extraction algorithm which uses the conversion between quaternions and Euler angles to achieve the global results is also employed. The external disturbance are eliminated by estimation update laws. Simulations illustrate the results.