In order to explore the reasons that urban residents'attitude are not matched by their actions and promote the implementation of low-carbon behavior, this empirical research examined what kind of low-carbon knowledge is more conducive to residents'low-carbon behavior. First, low-carbon knowledge was classified as system knowledge, action knowledge, and effective knowledge. Then, by extending the knowledge-attitude-behavior theory and introducing lowcarbon capability (LCC) as a variable on the basis of low-carbon intention (LCI), a dual mediation model for the mechanism of low-carbon knowledge on low carbon behavior was established. Finally, 1339 valid questionnaires were obtained and analyzed using structural equation model. A multiple group analysis was used to test the moderating effect of demographics. The results indicate that: (1) The difference of mechanism between the three types of low-carbon knowledge and low-carbon behaviors is one of the reasons that why urban residents'attitude are not matched by their actions. LCI and LCC have significant moderating effects on the relationship between system knowledge and residents'low-carbon behavior. Meanwhile, action knowledge can directly influence two kinds of low carbon behaviors or affect them indirectly through LCI. LCI is not affected by effective knowledge, but effective knowledge indirectly drives two kinds of low-carbon behaviors through LCC. (2) LCI driven by low-carbon knowledge is more often transformed into low-carbon purchasing behavior, while LCC is more often affected by low-carbon habitual behavior. Therefore, in order to form a long-term mechanism of low-carbon consumption and reduce the"rebound effect"of energy efficiency improvement, it is necessary to pay attention to the cultivation of low-carbon capability. (3) Gender, marital status, age, education level, and personal monthly disposable income have significant moderating effects on the relationship between action knowledge and two types of low-carbon behaviors. Relevant government agencies need to guide and promote the integration of knowledge and behavior among residents in lowcarbon comsumption according to the mechanism of different low-carbon knowledge.