Abstract: To address the monitoring needs of low-concentration multi-component hazardous gases in industrial environments and reduce the size of measurement instruments, a long-path gas absorption cell using the White cell structure was developed. This cell aims to lower the detection limit, enabling the detection of low-concentration multi-component hazardous gases. This paper discusses the design, working principles, and simulation results of the long-path gas absorption cell, as well as the setup of the optical experimental platform, selection of the infrared light source, and infrared pyroelectric detectors. Experiments based on this setup were conducted, and the least squares method was employed to derive concentration inversion models for various gases. These models were validated using different combinations of standard gases, and the relative errors of the experimental results were calculated. The results indicate that the designed multi-component hazardous gas online monitoring instrument can detect concentrations as low as 5 μL/L with a measurement error of ≤±5%F.S. (full scale), meeting the needs for low-concentration multi-component hazardous gas measurements.