The work aims to realize real-time monitoring of gas temperature, humidity, pressure and nitrogen concentration in airtight packaging box. The sensor chip board-level integration technology and the electrical signal airtight transmission technology were studied. The nitrogen concentration acquisition algorithm based on the oxygen sensor was derived. A gas state monitor was designed. Based on embedded processor and. NET framework interface, the design of the monitor was completed. Calibration tests of different parameters were conducted in the national standard laboratory. The measurement uncertainty of nitrogen concentration, temperature, humidity, pressure at confidence probability was 0.34%, 0.2 ℃, 1.3%, 0.05 kPa, respectively. Experimental results show that the device can collect the gas state parameters in the airtight packaging box and display them on the host computer interface in real time and stably. The measurement uncertainty meets the requirement of parameter accuracy. After matching with the sealed cabin, there is no pressure leakage after 12 d of airtight test.