Abstract: Benzene series emitted from indoor decorating materials seriously affect people’s health. In this study, an innovative helical membrane solid-phase extraction inlet was designed and coupled to a portable single photon ionization-time of flight mass spectrometry (SPI-TOF MS) for in situ and rapid detection of trace benzene series in air. A hollow fiber membrane (HFM) was applied to adsorb the benzene series, and the membrane material was polydimethylsiloxane (PDMS). In the membrane extraction device, the length of the HFM was prominently increased with the helical structural design of the HFM. The installation length of the HFM was as long as 150 cm, but the volume of the membrane extraction device was only （3.14×484×92） mm3. The problem with traditional membrane inlet that had a small membrane area was solved. The operating parameters of the membrane extraction device were optimized, which mainly targeted for the sampling flow rate, desorption temperature and enrichment time. As a result, the optimal sampling flow rate was found to be 600 mL/min, the optimal desorption temperature was 180 ℃ and the enrichment time was selected as 5 min. Under the optimal conditions, compared with the direct capillary sampling, the detection sensitivity of the benzene, toluene and xylene were enhanced 32.1, 71.8 and 129.9 folds within 14 min analytical period, respectively. The concentration range of 69.6-3 482.1, 82.1-4 107.1 and 94.6-4732.1 μg/m³ of the benzene, toluene and xylene standard gas were tested for quantitative analysis. As a result, the linear correlation coefficient (R²) of the three target compounds were all greater than 0.990 0. Based on the standard curves and the signal-to-noise (S/N) ratios, the limits of quantitation (LOQs, S/N=10) of the benzene, toluene and xylene were calculated as 33.3, 67.8 and 93.6 μg/m³, respectively, which were much lower than the legal limit of BTX in room air. In addition, 3 482.1, 4 107.1 and 4 732.1 μg/m³ standard samples for benzene, toluene and xylene were tested by this system for 8 cycles while the thermal desorption processes of each cycle were tracked. The relative standard deviation (RSDs) of eight individual analytical periods for the BTX were 3%, 1.7% and 2.4%, respectively, showed good repeatability. Finally, the whole system was used for analyzing laboratory air, and characteristic peaks of toluene, xylene, acetone, butanone and ethyl tert butyl ether (ETBE), et al were recognized in the mass spectrum. Based on the standard curves, the concentration of the toluene and xylene were calculated as 73.6 and 100.5 μg/m³. The size of the portable SPI-TOF MS was only （29×40×31） cm³ with a weight of 27 kg, which was prospectively applied for in situ and multipoint rapid detection of trace benzene series in indoor air.