High participation rates by the public in authority projects are key in increasing resident recycling levels. Understanding waste separation behavior is crucial to achieving sustainable waste management within such household-based schemes. To identify the driving forces behind the seldom-discussed kitchen garbage separation behavior, five psychological factors, namely, attitude, perceived behavior control, subjective norms, moral norms, and responsibility denial, are established. Our data originate from a social study of Beijing citizens conducted in July 2013 (n = 362). Through structural equation modeling, we find that moral norms are consistently the most important predictor of household kitchen waste (KW) separation behavior. Subjective norms have a larger effect on such behavior than responsibility denial. Data analysis shows that perceived behavior control contributes significantly and independently to the explanation of such behavior. By contrast, attitude towards KW separation is found to be significantly negatively correlated with separation behavior. In conclusion, the model with direct and indirect effects of psychological factors explains 50.3% of the variance in household KW source separation behavior. Implications of the results for the promotion of household KW separation programs are discussed.