Abstract: In the six letters with Ruge, the process of young Marx’s thought transformation has been relatively complete. Taking the correspondence between Marx and Ruge as a clue and referring to the texts of the young Marx in this period, the ideological coordinates for examining the thought transformation of the young Marx are formed. This paper provides a new perspective for clarifying the ideological relationship between Marx and Ruge, revealing the inner logic of the transformation of Marx’s thought. Taking Lugar’s influence on the change of Marx’s thought as the node, it can be seen that Marx’s thought transformation from religious criticism to political criticism to social criticism. Compared to the theoretical critique of the Young Hegelians, Marx turned to political criticism with more realistic significance and became a fellow traveler with Ruge. Marx discovered the power of the proletariat in his political critique and eventually took the road to communism through social revolution and their short-lived partnership collapsed. In this process, Engels’ political economy and Feuerbach’s materialist philosophy became the new fulcrum of Marx’s ideological development. Marx then embarked on the path of scientific socialism through the critique of political economy and became a practical materialist.