The present invention refers to a method for actuating semi-controlled valve that acts in synchronism with the compression cycles of an alternative compressor and to a system for actuating a multi-suction alternative compressor semi-controlled valve. Said method comprises at least a step of detecting at least one compression peak (1) in the course of at least one mechanical cycle (2) of the alternative compressor; and at least a step of switching the functional status of at least an alternative compressor semi-controlled valve (3) based on detecting at least one compression peak (1) in the course of at least one mechanical cycle (2) of the alternative compressor (5).