Abstract: The recent advances in the main clean processes to synthesize diphenylmethane diisocyanates (MDI) are reviewed，such as BTC method，condensation of aniline，reductive carbonylation of nitrobenzene，oxidative carbonylation of aniline，methoxycarbonylation of aniline，alcoholysis of N,N′-diphenyl urea and the coupling process. The coupling process not only has mild reaction conditions，simple operation，high atomic economy and low cost，but also promotes the mitigation and resource utilization of greenhouse gas CO2，and has the best commercialization prospect.