The accurate judgment of the principal contradiction facing Chinese society has always been the basic premise for the Communist Party of China to formulate a correct political route. In the past one hundred years, the CPC’s cognition of the principal contradiction in different periods, as a whole, has experienced an evolving from right to wrong, and then from wrong to right. Centered on the solution of the principal contradictions, the party has formulated five political routes in different historical periods in the past one hundred years, which re? veals the core clue of the continuous advancement of the centenary cause of the Communist Party of China, and presents a big picture of identifying the principal contradictions, clarifying the central tasks, formulating political routes and implementing policies and strategies. The exploration of the political route of the Communist Party of China in the past one hundred years and the profound grasp of the principal contradictions in the new era have provided valuable experience for the comprehensive construction of a modern socialist country.