A mass-balance means, used for a rotary microtome of the type that includes an object carriage carrying a specimen holder that holds the specimen to be cut, wherein the object carriage is driven to move up and down in a vertical path of the rotary microtome by a drive means, wherein the mass-balance means comprises: a connecting element, a first end of the connecting element being configured to be connected with a movable mass of the rotary microtome, wherein the movable mass includes all of the movable components of the microtome, especially the object carriage, the specimen holder, the specimen and other movable components such as a hand wheel or a fly wheel; characterized in that the mass-balance means further comprises: a gear set (20, 30) having a preset gear ratio, a first end of the gear set (20, 30) being connected with a second end of the connecting element; and an elastic element, the elastic element being pre-tensioned and adjustable, wherein a first end of the elastic element is connected with a second end of the gear set (20, 30) for moving along with a rotation of the gear set (20, 30), and wherein the second end of the elastic element is in use connected to a base frame of the rotary microtome, so as to balance the movable mass, wherein the gear set (20, 30) comprises: a driving disc (21, 31) connected with the second end of the connecting element; and at least two gears, wherein one of the at least two gears adjacent to the driving disc (21, 31) is fixed to the driving disc (21, 31) coaxially, another gear of the at least two gears adjacent to the elastic element is connected with the first end of the elastic element, wherein a connecting point of the first end of the elastic element and the one gear of the at least two gears adjacent to the elastic element is located in an edge of the one gear of the at least two gears adjacent to the elastic element, and wherein a connecting line of the connecting point and a center of the one gear of the at least two gears adjacent to the elastic element has an included angle α relative to a vertical direction, and during an operation of the mass-balance means, the included angle α ranges from 20° to 60°. a gear set (20, 30) having a preset gear ratio, a first end of the gear set (20, 30) being connected with a second end of the connecting element; and an elastic element, the elastic element being pre-tensioned and adjustable, wherein a first end of the elastic element is connected with a second end of the gear set (20, 30) for moving along with a rotation of the gear set (20, 30), and wherein the second end of the elastic element is in use connected to a base frame of the rotary microtome, so as to balance the movable mass, wherein the gear set (20, 30) comprises: a driving disc (21, 31) connected with the second end of the connecting element; and at least two gears, wherein one of the at least two gears adjacent to the driving disc (21, 31) is fixed to the driving disc (21, 31) coaxially, another gear of the at least two gears adjacent to the elastic element is connected with the first end of the elastic element, wherein a connecting point of the first end of the elastic element and the one gear of the at least two gears adjacent to the elastic element is located in an edge of the one gear of the at least two gears adjacent to the elastic element, and wherein a connecting line of the connecting point and a center of the one gear of the at least two gears adjacent to the elastic element has an included angle α relative to a vertical direction, and during an operation of the mass-balance means, the included angle α ranges from 20° to 60°. a driving disc (21, 31) connected with the second end of the connecting element; and at least two gears, wherein one of the at least two gears adjacent to the driving disc (21, 31) is fixed to the driving disc (21, 31) coaxially, another gear of the at least two gears adjacent to the elastic element is connected with the first end of the elastic element, wherein a connecting point of the first end of the elastic element and the one gear of the at least two gears adjacent to the elastic element is located in an edge of the one gear of the at least two gears adjacent to the elastic element, and wherein a connecting line of the connecting point and a center of the one gear of the at least two gears adjacent to the elastic element has an included angle α relative to a vertical direction, and during an operation of the mass-balance means, the included angle α ranges from 20° to 60°.