This research was based on the Lay Theory to discuss if the individual knowledge of consumers can influence the degree of trusting the global warming topic and give rise to the usage intentions and actual behavior of a low-carbon life. This research used the questionnaire investigation method, with 176 samples collected, and made regression analyses to verify the hypotheses. It was found that when people believe that an external environment can change, they will not agree that climatic variation is a false topic. However, they will hold reservations toward whether they can mitigate the change of the external environment. In addition, when people hold a skeptical attitude toward climatic variation, no intention for a low-carbon life will arise. Conversely, those thinking that it is possible to mitigate external environmental deterioration through sustainable acts will have more intention to engage in a low-carbon life. Further, people with the intention to engage in a low-carbon life often already practice relevant sustainable acts in day-to-day life. Lay theories predicted people's beliefs which further influenced people's different intentions and behaviors towards energy conservation and carbon reduction.