This paper presents a practical method to establish the kinematics model for the mobile modular manipulator. A tough issue is resolved by decomposing a given task into motions performed by both the manipulator and the mobile platform. A direct differentiation method is used to analyse the differential kinematics. Stability analysis of the mobile manipulator is performed to evaluate the possibility of tip-over; some stability criteria are established. Computer simulations are carried on a real mobile modular manipulator, and ideal results are received to show that the theoretical analysis is feasible and correct. © IMechE 2005.