Abstract: The design and structure of a smart gas cylinder valve cap coupled with a smart MEMS mass flow meter, an embedded iBeacon or RFID reader and a remote data transmission module, which is capable of formulating an Internet of Things (IoT) system, is demonstrated in the disclosure. The smart gas cylinder cap(s) can be directly used to replace the mechanical valve handwheel or directly attached to the top of the existing mechanical handwheel as a smart data relay, and the cap(s) can either be applied to a single or plural numbers of gas cylinders while the smart gas flow meter shall communicate with the smart gas cap as well as to relay gas consumption data to a designated data center or a “cloud” which can further interface with the users and suppliers of the gas cylinders.