Nowadays, hydrogenated nitrile rubber was mainly prepared by solution hydrogenation with noble metal catalyst, which would face two difficult influences of noble metal and organic solvent on hydrogenation process. Therefore this review mainly introduced the hydrogenation method of HNBR prepared by diimide reduction generated in-situ way in latex stage. NBR latex could be selectively hydrogenated by diimide generated in-situ through selecting hydrated hydrazine catalyst and latex as medium, which have effectively avoided tedious hydrogenation steps involved no need of large amounts of toxic organic solvents and noble metal catalyst. At the same time, the by-products of diimide reduction are nitrogen and water. It is an environmentally friendly and efficient method of selectively hydrogenation of diene polymer that also can simplify the hydrogenation process and save costs. There is a broad application area in automotive, petroleum, aerospace and military industry because of the high performance specialty of HNBR.