The present invention provides a control device and method for CO2 in a closed environment. The control device comprises a closed terrarium; a plurality of chambers are disposed at the top of the terrarium; one side, adjacent to the terrarium, of each chamber is provided with a switch for controlling whether the inside of the chamber communicates with the inside of the terrarium; the chamber is used for placing a CO2 adsorbent; a sensor is for detecting the CO2 content A1, CO2 production rate A2 and O2 content B inside the terrarium, and transmits A1, A2 and B to a processor; the processor derives an area S according to the received A1, A2 and B; a detecting unit is used to detect position of an animal in the terrarium and transmit the position a control unit; and the control unit adjuststhe switch such that the sum of the areas of openings at the bottoms of the chambers above the position matches the area S. The Control device and method have the advantages of safety, and high control precision.