Based on self-determination theory，this study establishes equity crowdfunding investors motivation model with intrinsic motivation as independent variable, extrinsic motivation as moderating variable, and decision to pledge as dependent variable. This study carries out exploratory factor analysis and binary logit regression analysis on the questionnaire data of a survey from 560 equity crowdfunding investors. The results indicate that: (1) Help motivation and trust motivation load in a common factor, name trust-based help motivation; (2) regarding to intrinsic motivation, trust-based help motivation and community motivation all have significant positive influence on the decision to pledge, expect for support motivation; (3) regarding to extrinsic motivation, rewards motivation has significant negative influence on the decision to pledge but the effect of economic returns is not significant; (4) economic returns and rewards motivation all have significant moderating effect on the relationship of trust-based help motivation and the decision to pledge, as well as on the relationship of community motivation and the decision to pledge.