A mid-infrared carbon dioxide(CO_2) sensor is presented for the application in greenhouse environment. An integrated multi-pass gas chamber and a dual-channel differential detection method are adopted to decrease response time and suppress environmental influence, respectively. An optical module is developed using a cost-effective wideband mid-infrared light source, a dual-channel pyre electrical detector and a spherical mirror, and the moisture-proof function is specially designed for enabling the application of this sensor in greenhouse with high humidity. Experiments are carried out to evaluate the sensing performance on CO_2 concentration. According to the experimental results, the limit of detection(Lo D) is about 3×10~(-5) with an absorption length of 30 cm. The relative detection error is less than 5% within the measurement range of 3×10~(-5)—5×10~(-3). Based on 10 h long-term stability measurement on 5×10~(-4) and 2×10~(-3) standard CO_2 samples, the maximum fluctuations are 1.08% and 3.6%, respectively. By using a 2.4 GHz wireless network communication system for remote monitoring and data recording, a field measurement of this sensor in a greenhouse is conducted, and good performance is proven in such circumstance. A mid-infrared carbon dioxide (CO_2) sensor is presented for the application in greenhouse environment. An integrated multi-pass gas chamber and a dual-channel differential detection method are adopted to decrease response time and suppress environmental influence, respectively. An optical module is developed using a cost-effective wideband mid-infrared light source, a dual-channel pyre electrical detector and a spherical mirror, and the moisture-proof function is specially designed for enabling the application of this sensor in greenhouse with high humidity. The limit of detection (Lo D) is about 3 × 10 -5 with an absorption length of 30 cm. The relative detection error is less than than 5% within the measurement range of 3 × 10 -5 -5 × 10 -3. Based on 10 h long-term stability measurement on 5 × 10 -4 and 2 × 10 -3, 3) standard CO_2 samples, the maximum fluctuations are using a 2.4 GHz wireless network communication system for remote monitoring and data recording, a field measurement of this sensor in a greenhouse is conducted, and good performance is proven in such circumstance.