The invention discloses a method for cooling a rolling bearing on line of a nuclear power station. The method comprises the following steps: detecting and determining whether the temperature of the rolling bearing reaches or exceeds a pre-warning value; examining and discriminating that the temperature rise of the rolling bearing is caused by overmuch lubricating grease; and purging a bearing chamber of the rolling bearing by virtue of compressed air, detecting the temperature of the rolling bearing after the purging, if the temperature of the rolling bearing decreases to a normal value, stopping the purging, otherwise, purging the bearing chamber of the rolling bearing again, and repeatedly carrying out the operations until the temperature of the rolling bearing decreases to the normal value. The method has the beneficial effects that the temperature of the rolling bearing can be decreased on line without halting, the time is saved, and great economic benefits are achieved.