Using the fundamental absorption band at the wavelength of 4.25 μm of carbon dioxide molecule, a differential mid-infrared carbon dioxide detection system was developed. The optical part of the system includes infrared thermal emitter, dual-channel pyroelectric detector and spherical mirror and the circuit part mainly consists of signal-processing, source-driving and main-control module. Simulating and optimizing the structure of the gas cell by using Tracepro software, eventually, the optical path of the gas absorption reaches 30 cm, and the performance of the system is improved. Preparing standard carbon dioxide gases with different concentration and investigating the sensing characteristics of system on carbon dioxide gas. Experimental results indicate that, the error between the measured concentration which are obtained by fitting curve and actual concentration is small, in the range of 0~5 000 ppm, the standard deviation of the measured concentration is less than 45 ppm, and that is less than 5 ppm under 500 ppm; the standard deviation of 2 hours long-term measurement concentration on the 0 ppm is about 2.8 ppm; the 1σ theoretical limit of detection obtained from the Allan variance is 2.5 ppm. Finally, each carbon dioxide sensor becomes a sensor node by adding wireless module nRF24L01 on each carbon dioxide sensor. Building a wireless sensor network in the chosen greenhouse. We have collected the carbon dioxide concentration and verified the performance of the developed sensor by filed application.