Microwave synthesis of poly-2, 2'-5, 5'-benzimidazole and poly-2, 5-benzimidazole are disclosed. The process of poly-2, 2'-5, 5'-benzimidazole is carried out by taking paraphosphoric acid PPA as solvent, condensation polymerizing under nitrogen protection, adding into 3,3'-diamino-benzidine, dissolving, adding into isophthalic acid, putting mixed liquid into microwave oven, programmed raising temperature at 300-500W, pouring reactant into deionized water, washing by water to become neutral, adding into saturated sodium bicarbonate solution, neutralizing, decompressing, extraction filtering, washing by water, washing by alcohol, drying and grinding into powders; process of poly-2, 5-benzimidazole is carried out by taking PPA as solvent, condensation polymerizing under nitrogen protection, agitating while heating to 200 degree, adding into 3, 4-diamino-benzoic acid, putting mixed liquid into microwave oven, programmed raising temperature at 300-500W, pouring reactant into deionized water, washing by water to become neutral, adding into caustic soda solution 1 mol / L, neutralizing, boiling at 100 degree for 6 hrs remove caustic soda, decompressing, extraction filtering, washing by water, washing by alcohol, drying and grinding into powders. It' efficient, has better radiant energy and shorter reactive time.