The invention relates to a knee joint rehabilitation device, comprising a base, a motor, a thigh connecting rod, a calf connecting rod, a guide rail, a first shaft and a second shaft. The thigh connecting rod, the calf connecting rod and an electric motor are arranged in pairs, the motor drives the thigh and calf connecting rods, a tie is arranged between the thigh connecting rods, one end of thethigh connecting rod is fixedly installed on the first shaft through a sleeve, two ends of the first shaft are provided with bearings, the first shaft is installed on the base through bearings, two sides of the base and corresponding positions of the first shaft are provided with bearing seats, and the other end of the thigh connecting rod and the lower leg connecting rod are connected together through a connecting rod pin. One end of the calf connecting rod is connected with the head of the base through a second shaft. At both end of that second shaft, rollers are arranged, and the rollers slide on the guide rails. The rehabilitation device of the invention is simple and portable, and easy to operate. The invention also provides a rehabilitation training method, which can train the knee joint to rotate in multiple directions, so as to obtain more sufficient exercise and promote the therapeutic recovery effect.