Ammonia absorb-type refrigeration and heat pump dual-purpose system and the cool and heat-supply method are relates to the refrigeration and heat pump system which use ammonia as actuating medium and use low grade heat energy and the cool and heat-supply method using the system, the system includes generator, finestiller, segregator, solution throttle valve, absorber, the first solution heat exchanger, the first solution pump, fluid storing groove, subcooler and ammonia throttle valve, the system also includes re-suction device, resolver, balance fluid pipe, the second solution heat exchanger and the second solution pump, among them the generator, the finestiller and the segregator are series connected, the ammonia gas outlet end of the segregator is connected with the ammonia gas inlet end of re-suction device through the ammonia gas pipelines, so the system highest pressure parameters in system is same with refrigerating mode basically under the premise of ensuring heat-supply temreature, thereby it can realizes two functions of refrigeration and heat pump safely according different seasons on the same ammonia water absorb-type system.