Abstract: Fu Ssu-nien’s thought was extremely exuberant in the May 4th Period, and he had discussed the issue of life earnestly. His discussion reflects his intellectual orientation of searching for certainty, and reveals his life and spiritual realm in the May 4th Period. Before the May 4th Movement, Fu Ssu-nien had began to explore the issues of society and life. However, the May 4th Movement provoked the contradiction between “nature” and “life” in his thought, so he decided to study psychology to search for certainty. Eventually, he gave up psychology with disappointment and began to carry out positive study of history and linguistics. Fu was under the influence of positivism in the “self-reforming” and the construction of the order of individual, society and history. He believed in positivism, while it could not provide the meaning of life. This spiritual crisis reflects the crisis of mentality in the May 4th Period.