A modular endoscope, comprising: a handle, a sheath tube and an endoscopic cannula, wherein the sheath tube comprises a first axial guide hole, a first joint pin disposed in the first axial guide hole and capable of axially moving in the first axial guide hole; a damping force is provided between the first axial guide hole and the first joint pin; the handle comprises a second axial guide hole, a second joint pin disposed in the second axial guide hole and capable of axially moving in the second axial guide hole; a damping force is provided between the second axial guide hole and the second joint pin, wherein the damping force between the first axial guide hole and the first joint pin and the damping force between the second axial guide hole and the second joint pin are both larger than a clamping force between the first joint pin and the second joint pin; the first joint pin matches and is directly connected to the second joint pin; the sheath tube matches and connects to the handle; the handle comprises a cavity and a tensioning mechanism is disposed in the cavity to axially tension the second joint pin; the endoscopic cannula comprises a flexible part extending out of the sheath tube and a rigid part fixed in the sheath tube; the flexible part comprises a steering wire, and the first joint pin is connected to the steering wire via a wire line; and the tensioning mechanism is connected to the second joint pin, wherein the sheath tube comprises a hollow conical sleeve comprising an axial hole, a cylindrical transition section, and a first joint sleeve; the endoscopic cannula is fixed in the axial hole of the hollow conical sleeve; the cylindrical transition section is disposed between the hollow conical sleeve and the first joint sleeve; the first joint sleeve comprises the first axial guide hole, and the first joint pin is disposed in the first axial guide hole; and the handle is a hollow structure and comprises a second joint sleeve; the second joint sleeve comprises the axial second guide hole, and the second joint pin is disposed in the second axial guide hole, wherein further the second joint pin comprises a shaft lever (14.1); the shaft lever (14.1) comprises a first end provided with two radially symmetrically disposed fixing pins (14.2); the first joint pin comprises a sleeve tube (13.1), and the first end of the shaft lever (14.1) is disposed in the sleeve tube (13.1); the sleeve tube (13.1) comprises a circumferential wall provided with two first locating slots receiving the two fixing pins (14.2); and the two first locating slots are L-shaped, and wherein the second joint sleeve is a cylinder comprising an inner wall having two symmetrically disposed first protrusions; the first joint sleeve is a cylinder comprising two second locating slots to receive the two symmetrically disposed first protrusions to axially fix the first joint sleeve and the second joint sleeve; and the two second locating slots are L-shaped. wherein the sheath tube comprises a hollow conical sleeve comprising an axial hole, a cylindrical transition section, and a first joint sleeve; the endoscopic cannula is fixed in the axial hole of the hollow conical sleeve; the cylindrical transition section is disposed between the hollow conical sleeve and the first joint sleeve; the first joint sleeve comprises the first axial guide hole, and the first joint pin is disposed in the first axial guide hole; and the handle is a hollow structure and comprises a second joint sleeve; the second joint sleeve comprises the axial second guide hole, and the second joint pin is disposed in the second axial guide hole, wherein further the second joint pin comprises a shaft lever (14.1); the shaft lever (14.1) comprises a first end provided with two radially symmetrically disposed fixing pins (14.2); the first joint pin comprises a sleeve tube (13.1), and the first end of the shaft lever (14.1) is disposed in the sleeve tube (13.1); the sleeve tube (13.1) comprises a circumferential wall provided with two first locating slots receiving the two fixing pins (14.2); and the two first locating slots are L-shaped, and wherein the second joint sleeve is a cylinder comprising an inner wall having two symmetrically disposed first protrusions; the first joint sleeve is a cylinder comprising two second locating slots to receive the two symmetrically disposed first protrusions to axially fix the first joint sleeve and the second joint sleeve; and the two second locating slots are L-shaped.