The invention relates to a preparation method of bipyridine, in particular to a preparation method of 2, 2'-bipyridine. The method includes: taking pyridine as the raw material, adopting supported nickel as the catalyst, carrying out dehydrogenation coupling reaction on pyridine under certain conditions, then conducting filtration, distillation, washing, chromatography, recrystallization and other separation steps to purify the product, thus obtaining a 2, 2'-bipyridine product. Compared with the traditional direct coupling method and halogen method, the method provided by the invention is safe and convenient for operation, and is environment-friendly.