This paper demonstrates Marx and Engels' theroy on establishing the proletariat party and the objective background of the formation of the proletariat party building theory.Seen from the internal factors,establishing the proletariat party and the formation of the proletariat party building theory were the result of the proletariat's development and expansion.Seen from the external factors,they were the product of the capitalist era and its parties and politics.It was these two factors that facilitated the e...