The invention discloses a binding assisting device for penetrating injury of knee joints. The device comprises a bottom plate, a worktable, a fixed support and a lifting support, wherein the worktableis mounted at the upper end of the bottom plate, a half-cylinder groove is formed in the middle of the upper end surface of the worktable, the worktable adopts a hollow structure, the fixed support is mounted at the front end of the upper end surface of the worktable, and the lifting support is mounted at the rear end of the upper end surface of the worktable. The problems that patients with penetrating injury of knee joints cannot straighten legs during binding, binding can only be performed on a bed, the limitation is higher, gauze winding is inconvenient, the legs of the patient are difficult to adjust, drugs easily fall due to shaking, the patient feels pain and the like in the prior art can be solved, and the device can realize assisted binding function on the patients with the penetrating injury of knee joints and has the advantages that the leg straightening state of the patient can be adjusted, the binding limitation is small, gauze is convenient to wind, the drugs cannot falland pain of the patient is not easily caused.