Carbon dioxide is the main greenhouse gas, and the research of carbon dioxide fixation and transformation is of great significance to global warming mitigation and environmental protection. Rapid development was made in the study of conversion of CO_2 in recent years, and biological methods of CO_2 fixation attracted much attention due to their mild reaction conditions and pollution-free. In this paper the immobilization of lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and oxaloacetate decarboxylase (OAADC), which were related with the conversion of CO_2, were preliminarily analyzed. First of all, the microcapsules were prepared with carbon nanotubes, chitosan and alginate to embed these CO_2 converting enzymes. And then the operating and storage stabilities of free enzyme were compared with those of the immobilized enzyme. The results showed that the operating and storage stabilities of the immobilized enzyme were significantly improved. This study would provide important reference for the transformation and application of CO_2.