With the natural gas widely used in the modern industry and daily life, gas safety issues become prominent. An air-tight property detector based on the principle of direct pressure with the C8051F350 MCU as the core is designed in this paper. It is controlled by the main and auxiliary systems in the form of hierarchical, and it is more flexible in detecting. The pressure is measured by the high accuracy differential pressure transmitter and the 24-bit A/D converter is used to deal with the small signals. The temperature compensation algorithm is introduced to improve the detection accuracy. As the uncertainty analysis shows that the experimental data meet the requirements.