The invention discloses a stair climbing power assisting device and a stair climbing power assisting method. The method includes the steps that a transmission mechanism comprises two groups of servo motors, worms, transmission shafts, worm wheels and chain wheels, the two groups of servo motors, the worms, the transmission shafts, the worm wheels and the chain wheels are oppositely arranged on the left side and the right side of a base, the worms are connected with output shafts of the servo motors, the worm wheels are matched with the worms to form meshing transmission, and the transmission mechanism further comprises chains meshed with the chain wheels on the two sides to form chain transmission; the transmission mechanism further comprises a sliding rail, a sliding platform and a chain transmission device, the upper side of the chain transmission device is provided with strip-shaped teeth matched with the upper side of the chain, and the lower side of the chain transmission device is provided with a small chain wheel matched with the lower side of the chain; and the transmission mechanism further comprises a folding rod, a handrail and an induction module mounted on the handrail, the induction module comprises a stress sensor, an acceleration sensor and a wireless module, the wireless module is connected with an induction controller, and the signal output end of the induction controller is connected with a driver of the servo motor. According to the stair climbing power assisting method, the walking aid can help the old to go upstairs and downstairs easily and carry heavy objects, and is humanized in design, safe and reliable.