A gas flow monitoring system based on NB-IoT technology was developed to address the issues of low measurement accuracy, limited functionality, and poor safety performance in traditional gas meters. The hardware aspect of the system employed an STM32 microcontroller as the main control chip and incorporated a specially designed thermal gas flow meter to accurately measure gas flow. Additionally, multiple sensors were integrated to enable real-time monitoring of temperature, humidity, gas concentration, and pressure in the gas environment. The software design utilized the FreeRTOS operating system. Leveraging NB-IoT technology, the system transmitted monitoring data to the OneNET cloud platform, allowing users to monitor gas usage in real-time through a dedicated mobile application. Experimental results demonstrated that the system achieved gas flow measurement ranging from 0.016 to 6 m3/h with a measurement error within ±1% and a repeatability of less than 2%. Furthermore, the system's wireless data transmission remained stable, effectively ensuring the accuracy and safety of gas monitoring.