The present invention relates to the field of sapphire crystal growth furnaces, wherein a purpose of the present invention is to provide a trisection disc weighing apparatus for a sapphire furnace. The trisection disc weighing apparatus comprises a small weighing sensor, a large weighing sensor, a weighing disc, top caps, a supporting point and an annular base, wherein the small weighing sensor, the large weighing sensor and the supporting point are equally fixed on the base and are respectively provided with the one hemispherical top cap, the heights of the three top caps are the same, and the weighing disc is arranged on the three top caps in a centering manner. The trisection disc weighing apparatus has the following characteristics that: the structure is stable, outside interference resistance is strong, measurement data is precise, and crystal weight measurements at different stages are precise with selections of the large measurement range and the small measurement range. With the present invention, the seeding process completion of the sapphire furnace is easily achieved, actual figure reference is provided for drawing speed control in the whole crystal growth process at the later stage, and ready work is provided for achievement of automated seeding detection and crystal growth.