A scalable multi-phase switching converter includes: converter modules, each including: a loop control unit, which generates a basic trigger pulse according to a feedback signal in master operation mode; and a switching control unit, which determines an operation mode and a corresponding phase serial order according to a setting signal received by a setting pin in a setting mode, and generates a multi-phase trigger pulse signal at a trigger pin according to the basic trigger pulse in master operation mode. The switching control unit receives the multi-phase trigger pulse signal at the trigger pin in slave operation mode. The switching control unit generates an ON-trigger pulse according to the multi-phase trigger pulse signal and the corresponding phase serial order. An ON-period determination unit generates a conduction control pulse according to the ON-trigger pulse to control a corresponding inductor. The trigger pins of the converter modules are coupled to each other.