The invention provides an enhanced-vapor-injection air conditioning system. The enhanced-vapor-injection air conditioning system comprises a second four-way valve (5) which is in tandem connection between an indoor heat exchanger (4) and an outdoor heat exchanger (3), wherein a first valve port of the second four-way valve (5) communicates with the indoor heat exchanger (4); a fourth valve hole communicates with the outdoor heat exchanger (3); a second valve hole communicates with one end of a primary path expansion valve (7); the other end of the primary path expansion valve (7) communicates with one end of a super-cooling heat exchanger (6); the other end of the super-cooling heat exchanger (6) communicates with a third valve hole of the second four-way valve (5); one end of a secondary path expansion valve (8) communicates with the super-cooling heat exchanger (6); and the other end of the secondary path expansion valve (8) is connected between the third valve hole and the super-cooling heat exchanger (6) or between the super-cooling heat exchanger (6) and the primary path expansion valve (7). The enhanced-vapor-injection air conditioning system provided by the invention can improve the operation effect under a refrigerating mode and a heating mode to certain extent through a simple system structure.