Abstract: By the application of the finite element method, the mechanical models of the bearing of small size mono-cone bits have been established,and the concrete equation of the distribution load P(θ) is derived in the region of the bearing contacting with conebit, and the mono-cone bit bearing design of the conventional concentrating load method is broken through, at the same time, the paper gives the series of the structure dimensions of the small size mono-cone bit and their yielding weight and design weight.