The invention relates to a refrigeration circulating system and an application thereof. The refrigeration circulating system comprises a condenser, an evaporator and an expansion valve. The refrigeration circulating system is characterized by also comprising a compressor unit, wherein the compressor unit comprises a capacity-controllable single-cylinder first rotary compressor and a capacity-fixed second rotary compressor, and the first rotary compressor and the second rotary compressor are simultaneously connected into the refrigeration circulating system; the first rotary compressor comprises a seal housing, and an electric motor part and a compressing mechanism part are arranged in the seal housing; the compressing mechanism part comprises a cylinder, a round piston, a slide spring, a crank shaft, a main bearing and a supplementary bearing, wherein the round piston is capable of making eccentric rotation in a compressing cavity of the cylinder, the slide spring abuts against the back part of a slip sheet, the front end of the slip sheet can be connected with the circumference of the piston, the crank shaft is used for driving the piston to rotate, and the main bearing and the supplementary bearing are used for supporting the crank shaft; and the first rotary compressor is provided with a pressure switching device. The invention has the characteristics of low manufacturing cost and wide application range, and improves the energy efficiency and the comfort of the air conditioner.