The article focuses on the position of the effect of science on secularization and tries to show why this effect of science on secularization by examining why. In order to answer the above question, the effect of the supporters of science on secularization was examined in detail and the issue was discussed from their point of view. Finally, in response to the question, what are the causes and mechanisms of secularization? It was concluded that the reason for the effect of science on the secularization of contradictions and incompatibility of "basic assumptions and beliefs", "consequences", "characteristics", "explanations" and "spirit" of science with religion. In this situation, it means that the existence of incompatibility between the above cases with the religion of science causes the secularization of society by reducing the need for religion or changing the attitudes and beliefs of individuals. That is, science, on the one hand, reduces people's need for religion and, on the other hand, causes a change in their attitudes and beliefs, and thus results in secularization.