This article first introduces the background and the basic concepts of link aggregation technology. It then describes the contents and principles of LACP. LACP state machine module controls the operation of the LACP. It is the core and key module to ensure LACP work effectively. Finally the LACP protocol state machine module function is implemented and optimized based on LACP and Finite state machine design method. In testing, the module operates normally. It can handle all circumstances correctly when the pro- tocol is running.