To understand the factors and their influencing mechanisms on PhD students' creativity, we propose an extended scientific and technical human capital (STHC) model to examine the structural relationships among different sources of social capital, psychological capital, and PhD students' creativity and to test the moderating role of gender, industry experience, and interdisciplinary experience on the structural model. Data are collected from 201 respondents enrolled in the Joint Training Pilot Project (JTPP) in 2010 and 2011. The results show that (1) university social capital has a significant direct influence on PhD students' creativity, while industry social capital has no significant direct effect; (2) psychological capital partially mediates the relationship between university social capital and creativity and fully mediates the industry social capital and creativity linkage; and (3) gender, industry experience, and interdisciplinary experience moderate several paths. Theoretical and practical implications are discussed, and recommended directions for future research are suggested.