The present invention discloses a high-strength R-T-B rare earth permanent magnet and a preparation method thereof. The magnet contains 0.3-1.5 wt. % of an element Zr, and a cast strip prepared through vacuum induction melting and melt spinning is treated at a high temperature to make the element Zr therein precipitate in a form of fibrous Zr compounds from R-rich phases, and the fibrous Zr compounds can be uniformly mixed with magnetic powder after hydrogen decrepitation and powder jet milling and mixing, and gradually grow into rod-like Zr compounds existing in the R-rich intergranular phases during the sintering of a green compact. By adjusting the content of the element Zr, sintering temperature and time and other process parameters, the morphology, size and distribution of Zr compounds can be effectively controlled, and the mechanical properties of the magnet can be improved by strengthening the R-rich intergranular phases without deteriorating the magnetic properties of the magnet.