The purpose of this study is to explore the alterations of brain functional connectivity among different hypercapnia using resting-state functional magnetic resonance imaging (rs-fMRI). 10 healthy males were enrolled in this study. A high-resolution T1WI image and BOLD-EPI were performed by a 3 Tesla MR scanner. The CO2 gas mixture (air, 3%, 5% and 7%) was given at the different hypercanpic for each experiment. Our results show that the brain functional connectivity in resting state is changed in hypercapnia. FC is gradual reduction as the increased CO2 fraction in the most primary functional networks, expect the executive control network.