Disclosed is a design assembly method for a gyro motor ball bearing with an outer ring having two grease storage circular grooves. A small grease storage circular groove (5) and a large grease storage circular groove are designed on inside end faces (7) arranged on the left side and the right side of a small semi-arc rolling passage (8) of the outer ring (1) respectively, wherein the curvature radius of the large grease storage circular groove is determined by the maximum length from a cross point of the small semi-arc rolling passage and the inside end faces to an inner chamfer surface of the outer ring, and the curvature radius of the small grease storage circular groove is one third to a half of that of the large grease storage circular groove. The asymmetric small grease storage circular groove and large grease storage circular groove are formed on the inside end faces of the outer ring and are filled with lubricating grease required by the ball bearing, one quarter of an arc rolling passage of an inner ring (2) is aligned with one side of the large grease storage circular groove before fitting of a cage (3) and a rolling ball (4) during assembly process, lubricating grease required by the ball bearing is filled with a limited space formed by the outer ring, inner ring and the cage to be used for a gyro motor, and accordingly the lubricating guarantee is provided for the gyro motor to prolong the service life.