The effective qualitative and quantitative detection of mixed components of volatile organic compounds (VOCs) with similar molecular structures has always been a challenge and hotpoint in the research. A novel quartz-crystal microbalance (QCM) nanocomposite sensor integrated with a surface-enhanced Raman scattering (SERS) detection platform for multi-component gas analysis was proposed and fabricated in this paper. MIL-100 (Fe)/PAN composite fibers were developed on QCM via electrospinning of polyacrylonitrile (PAN) and hydrothermal synthesis, addressing the integration issues of MIL-100 particles in devices while maintaining high specific surface area. The MIL-100(Fe)/PAN@QCM sensor can simultaneously collect QCM frequency responses and SERS spectra, enabling the quantitative and qualitative detection of toluene and benzaldehyde in mixtures. The linear response relationship between the frequency obtained by the QCM sensor and the concentration of toluene and benzaldehyde gases was in the range of 0-100 ppm, and the limits of detections were 0.57 and 0.86 ppm, respectively. Additionally, an algorithm, that considered the relationship among the QCM frequency response signal, intensity values of the characteristic peaks in the SERS spectra, and the gas concentration, was developed and applied to measure the mixed gases of toluene and benzaldehyde in the concentration range of 0-100 ppm. The relative standard deviations (RSDs) of spiked sample determinations were found to be in the range of 3-8%. This work provided a new method for the efficient and rapid detection of gas molecules with similar structures, which could be extended and applied to detect more multi-component gas mixtures.