Discovering the historic mission of the working class is one of the greatest contributions of Karl Marx. In a letter to Van der Mayer (1852), Karl Marx asserted that the discovery of the working class was the merit of French historians and he himself only discovered the historic mission of. the working class, found out the essential trends appearing the proletarian dictatorship due to the class struggle between the proletariat and the bourgeoisie. In "The Declaration of Communist Party", Karl Marx and Engels pointed out that the bourgeoisie not only had the weapons but also created people using the weapons against themselves. That means that the historic mission of the modern proletariat is an objective necessity. Over the past 160 years, the enemies of Marxism always distort or deny the standpoints of historical materialism, which has the problem of "historic mission of the working class". Therefore, protecting the viewpoints of Karl Marx about "the world historic mission of the proletariat" is the touchstone to distinguish between true, Marxists and disguised communists.