Multi airconditioning system and method for controlling the system

The invention provides, more specifically, the multi-unit air conditioning system and a control method for improving air-conditioning efficiency relates to a multi-unit air conditioning system. To this end, the present invention, a plurality of outdoor units (10,20,30); Connect to each other the refrigerant flow path of the outdoor unit is installed pressure difference eliminating tube 40 to relieve the refrigerant pressure difference between the outdoor unit; Then, the on-off valve (51,61) provided in the portion where the refrigerant flows to the outdoor units from the pressure eliminating pipe: providing a multi-unit air conditioning system and a control method which comprises a. Multi-unit air conditioning system, the pressure difference eliminating tube