The invention discloses a combined production steam synergistic device and method for a coal water slurry gasification furnace and a high-pressure boiler. The synergistic device comprises a coal waterslurry gasification furnace and a high-pressure fluidized bed boiler or a high-pressure pulverized coal boiler, a saturated steam outlet pipeline of the coal water slurry gasification furnace is communicated with a steam-clad steam outlet pipeline of a high-pressure fluidized bed boiler or a high-pressure pulverized coal boiler through a steam conveying pipeline, a valve is arranged on the steamconveying pipeline, and communication between the coal water slurry gasification furnace and the high-pressure fluidized bed boiler or the high-pressure pulverized coal boiler is realized through thecontrol valve. According to the method, the surplus overheating capacity of the boiler is utilized, and the boiler is suitable for saturated steam with the equivalent steam production pressure grade of the coal water slurry gasification furnace and the boiler, so that the effect of improving the steam quality and improving the utilization rate can be realized, meanwhile, only a part of the pipeline system is added, so that the original structure of the gasification furnace and the boiler is not changed, and once the gasification furnace is parked, by adjusting the load of the boiler, steam supply of the production system can be rapidly ensured, and safe and stable operation of the system is realized.