This paper presents a novel structure of hexrotor unmanned aerial vehicles which is fault tolerant against rotor failure. First, we define two types of hexrotors: Normal Hexrotor, and Variable CoM Hexrotor whose center of mass position (CoM) is movable during flight. Then, a fault-tolerance analysis method is presented based on existence of equilibria and controllability of linearized systems. Third, we prove that Variable CoM Hexrotor is fault tolerant due to its mechanical property nevertheless Normal Hexrotor is not. Finally, numerical simulations are conducted to validate the fault-tolerance analysis of Variable CoM Hexrotor.