R-T-B series permanent magnet and preparation method and application thereof

The invention discloses an R-T-B series permanent magnet and a preparation method and application thereof. The nitrogen content in the R-T-B series permanent magnet is X ppm, and X is more than or equal to 500 and less than or equal to 1300; the average grain size of the R-T-B series permanent magnet is D [mu] m, and D is more than or equal to-2.6 lnX + 20 and less than or equal to-2.3 lnX + 19.6; the R-T-B series permanent magnet comprises main phase grains and a grain boundary phase; the main phase crystal grains comprise R2Fe14B; the grain boundary phase is distributed among the main phase grains; the R-N enrichment region in the grain boundary phase accounts for less than 10% of the volume fraction of the grain boundary phase. According to the R-T-B series permanent magnet, the nitrogen element is evenly distributed at the grain boundary, NdN agglomerates are not formed or the content of the NdN agglomerates is extremely low, and therefore the coercive force Hcj of the magnet is improved, high-temperature