The utility model provides a lubricating oil system for a steam-driven water feeding pump. The lubricating oil system comprises a lubricating oil pump, an energy accumulator, an oil cooler, a low-oil pressure low switch and a low-oil pressure switch. A pipeline of a bearing oil inlet of the steam-driven water feeding pump is provided with a pressure leading point of the low-oil pressure low switch; the low-oil pressure low switch is electrically connected to a control device; the energy accumulator is connected with an main oil pump in parallel and is connected to a pipeline between the main oil pump and the oil cooler by a pipeline; the pressure leading point of the low-oil pressure low switch is arranged at an outlet of the lubricating oil pump; the low-oil pressure switch is electrically connected with the control device. According to the lubricating oil system for the steam-driven water feeding pump, a manner of arranging the pressure leading point of the low-oil pressure low switch on an oil supplying pipeline at the bearing oil inlet of the steam-driven water feeding pump is adopted so that the accurate detection of a pressure of lubricating oil entering a bearing can be ensured and a pump jumping movement is done in time when the oil pressure of the lubricating oil entering the bearing reaches a low condition. The energy accumulator can prevent oil pressure fluctuation caused by switching the lubricating oil pump and avoids pump jumping incorrect movement caused by the fluctuation of the oil pressure.