Abstract: The aging population and declining birth rates are becoming increasingly prominent in China, necessitating the need to enhance the fertility willingness among the eligible population to increase the birth rate. This article is based on interviews conducted with 37 "post-90s" individuals from various regions across the country. By utilizing grounded theory and mixed research methods, it aims to not only summarize and identify the main factors influencing fertility intention but also explore in-depth the combined impact patterns among these factors. The study reveals that the fertility intention of the "post-90s" generation is shaped by three main factors: economic, social, and cultural. These factors can be further classified into four types of combined patterns: comprehensive influence, development-oriented, independent and autonomous, and culturally-driven. The study also identifies three major effects among the factors influencing fertility intention: economic dominance, interconnected factors, and cultural amplification. Subsequently, the study conducts heterogeneity analysis based on gender, urban-rural divide, and marital status. In light of the research findings, the study proposes policy recommendations such as universal access to public resources, optimization of the fertility support system, heterogeneity-based classification of fertility policies, and the creation of a supportive and friendly environment for childbirth.