The invention discloses a method for reducing the molten steel nitrogen-increasing amount during a continuous casting process, and belongs to the technical field of steelmaking. The method comprises the steps of before continuous casting, adopting inert gas for replacing an atmosphere in a tundish, sealing the tundish, and ensuring that the oxygen content in the tundish is less than 0.1 percent; before casting per charge, sealing a bowl rim part of a long nozzle, utilizing an oxygen lance for purging a bowl rim part of a long nozzle of a big ladle during a continuous casting process, and ensuring that the inner part of the bowl rim is clean; after casting the big ladle, when the weight of molten steel injected into the tundish reaches 30 to 40 tons, adding a covering agent with high alkalinity, and covering a molten liquid level of the whole tundish through the covering agent; during the continuous casting process, ensuring that the long nozzle is inserted into a position 100 to 200mmbelow the molten steel level, casting, and enabling the long nozzle of the big ladle to align at a down nozzle of a steel ladle without inclination; and during a stable casting process, keeping the insertion depth of the long nozzle into the molten steel to be more than 200 mm. According to the method, the acceptability of the continuous casting molten steel nitrogen-increasing amount is effectively controlled, and the product quality and the stability are greatly improved.