The　most　basic　understanding　for　a　new　mechanism　is　to　realize　its　mobility.　But　there　is　little　theory　about　mobility　of　hybrid　mechanism　in　kinematics.　Due　to　the　complexity　and　particularity　of　hybrid　mechanisms,　the　mobility　of　hybrid　mechanisms　cannot　be　obtained　based　on　traditional　methods.　In　the　paper,　the　constraint　and　mobility　of　a　dendritic-hybrid　mechanism　is　analyzed　based　on　screw　theory.　The　complicated　loops　in　the　dendritic-hybrid　mechanism　are　regarded　as　generalized　kinematic　chains,　which　can　simplify　the　hybrid　mechanism　and　correctly　receive　the　number　and　characteristic　of　mobility.　©　(2013)　Trans　Tech　Publications,　Switzerland.