The invention discloses an oceangoing vessel 
ballast water processing method. According to the method, air over the 
ballast water in 
ballast water chambers is evacuated by an 
inert gas, the ballast water in the ballast chambers is pumped out of the ballast chamber, the ballast water is subjected to blow-off mixing by the 
inert gas to generate a physical reaction, a soluble 
inert gas is merged into the ballast water when 
oxygen in the ballast water is sucked out, and the processed ballast water is discharged into the ballast water chambers. A device of the method comprises the ballast chambers, ballast pumps, Venturi ejectors and an 
inert gas generator. The ballast 
water processing method of the invention, which is a physical method, needs no extra 
chemical agents or relevant dosing devices; the physical reaction can be directly generated in the Venturi ejectors, and no filter devices are needed before the reaction generation, so time-cost regular cleaning is not needed, the 
water flow is not influenced, the 
discharge time is reduced, and the chambers are protected from oxidation 
corrosion, thereby the reliability of the ballast 
water processing effect is guaranteed; and the method of the invention, which has a very good practicality, can generate very good 
economic benefits and 
social benefits.