Graphene has been widely used in gas-sensing applications due to its large specific surface area and strong adsorption ability. Among different forms of graphene used as gas-sensing materials, reduced graphene oxide is one of the most convenient and economical materials to integrate with Si-based electronics, which is very important to graphene-based gas sensors. In addition, the stacking structure of graphene oxide flakes facilitates absorption and detection of gas molecules. Based on reduced graphene oxide, a highly sensitive and portable gas-sensing system was demonstrated here. Solution-based graphene oxide was cast on a chip like a TF memory card and then reduced thermally. A signal acquisition system was designed to monitor resistance variation as a sign of gas concentration. This miniature graphene-based gas sensor array demonstrates a new path for the use of graphene in gas-detection technologies. And the creation of a sensitive and portable graphene gas sensor also shows great potential in fields such as medicine and environmental science.