An air conditioning system (1) includes an outdoor subsystem, an indoor subsystem and a power module (3) for driving a cooling medium. The outdoor subsystem is configured with a plurality of parallel branches (4) and said branches (4) comprise a branch inlet and a branch outlet, each branch (4) is configured with an outdoor unit (5) and a first control valve (6). The air conditioning system includes a controller (7), a first pressure sensor (8) and a second pressure sensor (9), the controller (7) comprises a first pressure difference determination module that communicates with the first pressure sensor and the second pressure sensor, and a first control module of the first pressure difference that communicates with the first pressure difference determination module and the first control valve (4), where the first pressure difference determination module determines the pressure difference between the outlet and the inlet of the branches.