Gas odorization is an important step in ensuring the safe use and transportation of gas. It is directly related to whether users can detect gas leaks in the first time. Online detection of tetrahydrothiophene concentration in the gas pipeline network is very important to ensure that the concentration of odorants at the user end is qualified. This article focuses on the problem of online detection of tetrahydrothiophene concentration in gas pipeline networks. A low-cost and high reliability online detection instrument is designed with MSP430 as the control core and electrochemical sensors as the detection method. Firstly, the cross interference characteristics of electrochemical sensors in detecting mixed gases were analyzed, and a mathematical model of cross interference was established. An optimization scheme was proposed to address the disadvantage of electrochemical sensors being prone to poisoning during online detection. Secondly, the hardware and software parts of the detector were developed. In addition, the detector adopts a dual explosion-proof housing design to ensure its safe use in gas environments. Finally, calibration and performance verification experiments were conducted on the detector in a laboratory environment, and a comparison experiment with a gas chromatograph was completed on site. The experimental results show that there is a good linear relationship between the true value and the measured value of the tetrahydrothiophene online detector designed, and the degree index R2 of the linear trend fitting is 0.996. The detector has shown good response performance in response time, Stability, repeatability, high and low temperature alternation, and the influence of gas source pressure test in the calibration experiment, with a range drift of 0.7%, repeatability RSD of 1.88%, indication error of 1.10%, and detection accuracy of 4.0 level. It can realize accurate measurement of tetrahydrothiophene concentration under gas environment with pressure 0.1~0.3 MPa and temperature -10 ℃~40 ℃. To solve the problem of gas pipe network tetrahydrothiophene concentration detection provides a scientific and reliable basis and means to ensure the safe operation of the gas pipe network and gas users’ life and property safety is of great significance.