The present invention relates to a joint mechanism (100), a method for controlling the joint mechanism (100), a multi-arm device (200) including the joint mechanism (100), and a robot. The joint mechanism (100) comprises: a base (4) having a pivot shaft (41); a swinging arm (1) having a first end (11) mounted on the pivot shall (41); a first driving member (2) and a second driving member (3) mounted on the pivot shall (41) for interacting with the swinging arm (1) through magnetorheological fluid; and a first electromagnetic component (22) and a second electromagnetic component (32), configured to change phase state of the magnetorheological fluid. The first driving member (2) and the second driving member (3) can selectively drive tire swinging arm (1) to rotate along a first direction or a second direction.