Using longitudinal data from Jiangsu Fertility Intention and Behaviour Study (JFIBS) from year 2007 and 2010, this study analyses the fertility intention and behaviour of women who are qualified to have two children from a psychosocial point of view. Based on the Theory of Planned Behaviour, the theoretical framework from fertility intention to fertility behaviour is reconstructed. By observing the phenomenon from the micro-level, the gap between female fertility intention and behaviour and its associated factors are studied. The result shows that, given the situation of being qualified to have two children according to the government's birth control policy, when faced with the choice of whether to have a second child or not, people tend to make their decisions rationally. Attitudes towards fertility, subjective norms, and perceived behaviour control all contribute significantly to the discrepancy between fertility intention and behaviour. In addition, the formation of a concrete birth plan is a major driving force for translating fertility intention into action.