The invention pertains to the technical field of 
rare earth magnetically hard material, in particular to a multi-main-phase Nd-Fe-B type permanent 
magnet with high 
crack resistance and high coercive force and a preparation method thereof.A final 
magnet contains multiple differently-sized hard-magnetic main-phase particles having different anisotropic fields HA. Different main-phase particles account for different volume fractions and are differently distributed, wherein Nd denotes a red earth element having the most content based on the 
mass percent. According to 
mass percent, the 
chemical formula of the permanent 
magnet is expressed as (Dd, Re) aFe100-a-b-cBbTmc. By respective selection, different types of main-phase materials such as (Nd, Pr)-Fe-B, (PR, La, Ce)-Fe-B, (Dy, Tb, Ho, Gd, Er)-Fe-B in the ratio of 2:14:1 in order to prepare corresponding coarse 
magnetic powder, thin 
magnetic powder and magnetic nanocrystalline 
powder. Power is utilized for absorbing 
hydrogen and controlling 
oxygen. Liquid-phase 
sintering technology on the pressurized condition at low temperature is adopted for preparation. The multi-main-phase Nd-Fe-B type permanent magnet with high 
crack resistance and high coercive force and the preparation method thereof have following beneficial effects: a large piece of magnet does not easily have crack; 
crack resistance of the magnet is improved; high coercive force and high 
magnetic energy product are obtained; and the preparation technology is suitable for scale production in 
engineering.