Objective To introduce the technical method and clinical application effect of arthroscopic assisted distal locking of femoral intramedullary nail through bone window。Methods A total of 12 patients with femoral shaft fracture in our hospital from January 2019 to November 2019 were selected and treated with that surgical method. The arthroscope was extended into the tissue space at fracture location, and the fracture was reseted. After the intramedullary nail smoothly enters the distal medullary cavity, extend the arthroscope into the space between the periosteum and muscle in front of the distal femur, drill the cortical bone to form a bone window, place the rod to the platform of intramedullary nail through the bone window, and then smoothly place the distal locking screw. The fracture healing was followed up and observed.Results All indicators related to plasma osmotic pressure before and after operation P > 0.05, and the difference had no statistical significance. It can be considered that no postoperative complications caused by arthroscopic operation such as water intoxication and electrolyte imbalance occurred. The distal locking time of the operation was 24.1 ± 7.33 (min), the number of distal locking fluoroscopy was 3.0 ± 0.95, 100% success rate of initial locking of distal locking screw，and the fracture ends healed normally in all 12 patients.Conclusion The surgical method of arthroscopic assisted distal locking of femoral intramedullary nail through bone window is safe, and can significantly shorten the operation time, reduce the number of use of C-arm machine, and simplify the distal locking operation.