The invention discloses a staged baking process for water content in a pole group of a lithium ion battery, which comprises the following steps: S1, sending a battery cell into an oven, heating the oven and vacuuming; S2, adjusting the temperature of the oven to 90-100 DEG C and baking for 10-20 min under the vacuum degree of 100-200 Pa, introducing nitrogen to adjust the temperature to normal pressure, and baking for 10-20 min at the temperature of 90-100 DEG C; S3, repeating S2 for 8-12 times; S4, vacuuming the oven to 100-200 Pa, keeping the temperature of 90-100 DEG C, baking for 25-35 min, introducing nitrogen, adjusting the pressure to normal pressure, and keeping the temperature of 90-100 DEG C, baking for 10-20 min; S5, repeating S4 for 5-6 times; and S6, vacuuming the oven to 100-200 Pa, stopping heating, and cooling. The staged baking process for the pole group water of the lithium ion battery can reduce the baking time of the battery cell and the water content in the pole group of the battery core.