A novel in-pipe micro robot providing stable and accurate locomotion inside a tubular structure with diameters ranging from 16 mm to 18 mm is presented in this paper. Driven by impulsive voltages, deflections of the piezoelectric bimorphs are generated and then converted into translational locomotion by the principle of the Impact Drive Mechanism (IDM). Theoretical analysis of the proposed system is performed based on a simplified mechanical model. Then dynamic simulations of the dynamic behavior are performed. Finally, an experiment is conducted to investigate the moving ability of this device. The results demonstrate that a maximum translational velocity of 3.5 mm/s can be obtained under an impulsive driving voltage with peak value at 50 V and frequency of 1100 Hz. Both theoretical analysis and experimental trials prove that the principle of IDM actuated by piezoelectric bimorphs is feasible and robust for achieving accurate locomotion of the micro robot in pipes with diameters of less than 20 mm. A novel in-pipe micro robot providing stable and accurate locomotion inside a tubular structure with diameter ranging from 16 mm to 18 mm is presented in this paper. Driven by impulsive voltages, deflections of the piezoelectric bimorphs are generated and then converted into translational locomotion by the principle of the Impact Drive Mechanism (IDM). Theoretical analysis of the proposed system is performed based on a simplified mechanical model. Then dynamic simulations of the dynamic behavior are performed. Finally, an experiment is conducted to investigate the moving ability of this device . The results demonstrate that a maximum translational velocity of 3.5 mm / s can be obtained under an impulsive driving voltage with peak value at 50 V and frequency of 1100 Hz. Both theoretical analysis and experimental trials prove that the principle of IDM actuated by piezoelectric bimorphs is feasible and robust for achieving accurate locomotion of the micro robot in pipes with diameters of le ss than 20 mm.