The invention discloses an auxiliary steam heat-supplying system for a steam turbine generator unit. The auxiliary steam heat-supplying system comprises two auxiliary steam headers; the auxiliary steam headers are connected with steam supplying main pipelines, steam-supplying pneumatic adjusting valves are arranged between the steam supplying main pipelines and the auxiliary steam headers, and thetwo auxiliary steam headers are connected with a heat supplying pipeline through a heat supplying piping; the heat supplying pipeline is connected with a steam supplying attemperator, the attemperator is connected with a temperature-reducing water pipeline and a steam supplying pipeline, and the temperature-reducing water pipeline is connected with a steam front pump outlet A, a steam front pumpoutlet B, a steam pump outlet A and a steam pump outlet B; water drainage points are arranged on the heat supplying piping and the steam supplying pipeline, and the steam supplying pipeline is connected with a drainage pipeline; and the steam supplying pipeline is further connected with a first semaphore steam-supplying pipeline and a second semaphore steam-supplying pipeline and finally connectedwith a coal-removing chemical pipeline. Energy consumption can be reduced, operation economy and reliability are improved, meanwhile, the temperature reducing process can be controlled and adjusted,and thus the system is simple, stable and reliable.