Barrel type gear couplings are improved from spur type couplings. The major elements are two barrel-type external gear sleeves and a pair of internal gear rings. The angular force is transferred by the engagement of the internal and external gears. And the relative bit shifts of the two axles are compensated by the axial swing (angular displacement) for the barrel type external gear sleeves inside the straight-toothed internal gear ring. The bigger the linear barrel shape, the bigger the angular displacement. The maximum is 6, however 1˚ 30´-3˚ is gene-ally recommended (1˚30´ is adopted in this catalog) the contacting between gear teeth is increased because of the design of linear barrel shape. Thus entitled the barrel type gear couplings with the features of bigger driving capability, bigger angular displacement, smoother driving, higher efficiency and longer service life, etc. Barrel type gear couplings are widely used as driving parts for metallurgical machinery, heavy machinery, mining machinery and handling equipment.