To　solve　the　complex　and　couple　problem　of　the　hybrid　mechanism,　an　equivalent　method　of　generalized-kinematic-chain　was　put　forward　to　obtain　the　mobility.　Based　on　the　screw　theory,　the　constraint　and　mobility　of　a　dendriform-hybrid　mechanism　was　analyzed　using　the　method　of　generalized-kinematic-chain　replacement,　and　the　complicated　mechanism　was　transferred　into　a　simply　mechanism,　thus　the　correct　mobility　was　obtained.　Result　shows　that　the　method　can　effectively　simplify　the　structure　of　a　hybrid　mechanism,　and　provides　a　certain　theoretical　basis　for　further　analysis　of　complex　coupled　mechanisms.