The invention mainly aims to provide a preparation method for a sintered neodymium iron boron (NdFeB) permanent magnet with both high coercivity and an excellent magnetic property. In the technical scheme, the preparation method for the sintered NdFeB permanent magnet comprises the following steps: (1) fetching NdFeB raw material powder, and soaking in a treatment agent formed in a way that the oxide or the fluoride of rare earth dysprosium is evenly dispersed in a solvent, wherein the concentration of the oxide or the fluoride of the rare earth dysprosium is 0.01-0.1g/ml; (2) subsequently, performing ultrasonic treatment on a mixture obtained in the step (1); (3) subsequently, taking out the magnetic powder of which the surface is formed with a coating from treatment agent solution and drying; (4) putting the dried magnetic powder in a vacuum heat treatment furnace for heat treatment; (5) then, orienting the evenly mixed powder in a magnetic field and performing compression moulding;and (6) putting a green compact in a vacuum sintering furnace for sintering, and then, performing secondary heat treatment to obtain the sintered magnet. According to the preparation method provided by the invention, the oxidation resistance of the prepared magnetic powder is greatly improved in the follow-up orientation compression process and the sintering process, and a rare earth boundary layer is formed on the grain boundary of a final magnet, thereby, the coercivity of the magnet is greatly improved, and simultaneously, obvious negative effects are not generated on other magnetic property parameters of the magnet, such as residual magnetism, magnetic energy product.