The essence of philosophy is about worldview and methodology, which is the foundation of guiding the development of all scientific undertakings. Marxist philosophy is a theory about the general law of the development of nature, society and thinking. It is the unity of materialism and dialectics and also the unity of scientific worldview and methodology. The two books, On Practice and On Contradiction, are the symbolic achievements of Mao Zedong Thought. They are the models of the unity of Marxist worldview and methodology, and they are also the product of the combination of Marxism and China’s specific situation. To learn Xi Jinping’s thinking on strengthening the armed force well, we must make great efforts to master the scientific methodology of strengthening the military and winning wars. That is, when pondering and facing the military problems, we must resolutely implement the epistemological and methodological principles contained in On Practice and On Contradiction, and constantly absorb scientific wisdom and theoretical power so that we can carry out the spirit of “unity of knowledge and action” in our work.