With the focus on one kind of mirror milling system consisting of two hybrid robots, the canonical forward and inverse kinematic model of the mirror milling system is developed by the vector method, in which the forward kinematic has the advantage of high computational efficiency and accuracy compared with the solution method using the Newton iterative method. A method for generating mirrored machining path is proposed, which specifies the positional relationship between the reference coordinate systems of two hybrid robots, and calculates the mirrored symmetric tool and support head paths by setting the desired machining wall thickness of the thin-walled structural part. Two methods for executing mirrored machining path are proposed by employing 10-axis linkage and dual 5-axis linkage respectively. The latter has the features of reconfigurability and modularity compared with the former, which supports single-machine operation of the milling or supporting robot, and satisfies the needs of rapid on-site arrangement and efficient collaborative machining of single or multiple machines in a large workspace. In order to verify the correctness and effectiveness of the proposed kinematic model and methods for generating and executing machining paths, experiments of machining a large scale thin-walled structural component are carried out. The experimental results show that the error of the machined wall thickness can be guaranteed within ±0.18 mm.