A ureteroscope (13), comprising a field of view lens (6), a channel opening (7), a lens tube (5) and an operating handle. An outer wall (10) of the lens tube (5) is provided with a groove (8), thereby maintaining unobstructed water drainage, and balancing water inflow and outflow. The groove (8) can also keep the field of view clear during surgery, reducing water pressure within kidneys and a ureter, thereby preventing postoperative febrile bacteraemia. A front end opening of the lens tube (5) inclines upwards. An eyepiece (1) moves behind the opening, it being beneficial to enter a ureter opening and insert a catheter and an instrument in the field of view, thereby preventing damage to a ureter wall. A tube wall of the lens tube (5) is externally provided with a drainage tube (11) having a drainage hole (14), the drainage tube (11) being capable of moving along the lens tube outer wall (10). The drainage tube (11) forms a drainage channel with a lens body outer wall, and is provided with a switch valve (12). During uninterrupted surgery, water and urine retained in a bladder is also discharged.