The invention discloses an assistant exoskeleton ankle joint joining device which is applied to the ankle joint joining between an exoskeleton crus and a sensing shoe. The lower end of a crus (11), a taper sleeve (7), a joint bearing (9) with three rotational freedom degrees and a vertical shaft (2) are connected in series through a lateral hinge pin (1), so that the lower end of the crus is connected with the joint bearing and the vertical shaft, and an exoskeleton can be used for stimulating the three rotational freedom degrees of a human ankle joint. Shock-reducing rubber and reset rubber are arranged at the same time so as to realize buffering and energy absorbing functions, and an additional elastic reset force can be provided for rotating the exoskeleton ankle joint, so that man-machine stability is increased; and the crus is connected through a hinge pin, and the sensing shoe is connected through a bolt, so load transfer can be smoothly realized.