The utility model belongs to a medical instrument which is applicable to a convenient practical guiding device of auxiliary machinery when a microwave knife is used to cure a tumor. The medical instrument is composed of a base, a support, an angle modulation frame, a guiding groove installed on the angle modulation frame, a guiding groove of the microwave knife and the like elements. The angle modulation frame is fixed on the round base and has two hinge positions of the support, the up and down and the high and low can be adjusted according to the differences of therapeutic parts and the fat and thinness of patients, and the left and right can be adjusted by a chute disposed at the upper end of the support. The upper end of a fan-shaped angle modulation frame is provided with an arc chute, a screw bolt is fixed at the lower end of the fan-shaped angle modulation frame, and the screw bolt penetrating an upper chute on the support is fixed with the upper chute via a locking screw nut. A long cylindrical guiding groove with an axial through-hole is hinged and arranged on the angle modulation frame via a pin shaft, a traversing circular column is disposed on the guiding groove, and the traversing circular column is connected with the arc chute via a screw nut by which the angle is adjusted. The utility model has the advantages of practicability and scientific characteristic, and is small, portable, and foldable, further the occupation space is small, the operation is simple, and the practicability is high and the like. The utility model is worth to be promoted and applied in clinical medical science.