Dual-comb spectroscopy is an important tool for performing high-resolution spectral analysis. However, its coherence depends on complex and huge frequency-locking and feedback systems. Thus, the implementation of this technique is expensive and the system is sensitive to environmental disturbances; consequently, the applications of this tool are limited. A dual-comb system based on an electro-optic frequency comb has the advantages of a simple device, frequency agility, high coherence, and conduciveness to field applications. However, its accuracy and real-time performance for concentration inversion in gas detection applications still need to be verified. Therefore, a highly coherent electro-optic dual-comb system was constructed in this study. The absorption spectra of CO and CO₂ were measured by using a multipass gas cell. The results are consistent with the simulation data of the HITRAN database. The spectral resolution reaches 200 MHz, and the single refresh time is only 4 μs. The concentration uncertainty of CO₂ absorption peaks is reduced to 2.86% by concentration inversion and multipeak fitting. In addition, the real-time performance of the system for monitoring the concentration of a gas mixture is verified through the rapid detection of the CO absorption spectrum. The system is expected to be applied to the real-time monitoring of the fault characteristic gases of power equipment.