Based on two dimensions of extrinsic-intrinsic and self-centered-community-related motivation and self-determination theory (SDT), this study proposes four important tourist photo-sharing motivations (enjoyment, altruism, self-expression, and social relationship) and built a theoretical model to reveal the mechanism of tourist photo-sharing motivation influencing tourist subjective well-being (SWB). The results show that extrinsic self-centered motivation (self-expression) positively affects intrinsic self-centered motivation (enjoyment), while extrinsic community-related motivation (social relationship) positively affects intrinsic community-related motivation (altruism). Two intrinsic motivations have significant impacts on tourist SWB. The moderating effects of social support present a complex picture, which can be explained by SDT. Implications were also discussed.