The invention discloses a single-lamp energy-saving control system and control method based on soft hand-off and multi-shift voltage regulation. The control system comprises a microprocessor, wherein the microprocessor is in communication with a self-coupling voltage reduction module and is further in communicated with an intelligent concentrator through a power line carrier communication module, the microprocessor is used for acquiring running data of a streetlamp and transmitting the running data to the intelligent concentrator, the running data is uploaded into a master station server by the intelligent concentrator, and the microprocessor detects a running state of a self-coupling transformer through the self-coupling voltage reduction module, and receives a control instruction of the intelligent concentrator to carry out soft hand-off on the self-coupling transformer so as to achieve control on a switch lamp and control on multi-shift stable voltage regulation. With the adoption of a soft hand-off technology, the switching reliability can be effectively improved, uninterruptable voltage output is ensured, and a phenomenon that a high-voltage sodium lamp is turned off caused by instant voltage drop is avoided.