Abstract: The chloride ion penetration performance of basalt fiber (BF) - polyacrylonitrile (PAN) hybrid fiber concrete was investigated under real sea exposure and indoor dry-wet cycling conditions. The influence of fiber blending methods (single BF, single PAN and hybrid BF-PAN), fiber volume fractions (0.2% and 0.4%) and exposure age on the chloride ion transport behavior was analyzed. Based on the classical Fick's second law, the changes of surface chloride ion concentration (C_s) and apparent chloride ion diffusion coefficient (D_Cl) of fiber concrete were discussed, and the corresponding time-varying models were established. The similarity analysis of chloride ion penetration performance under real sea exposure in the tidal zone and indoor dry-wet cycling conditions was carried out. The results show that the free chloride ion content in fiber concrete increases with the extension of exposure time under different exposure conditions. In this study, the fiber concrete with 0.2% BF (BF-1) shows the best resistance to chloride ion penetration, after exposure to underwater zone for 90 days, the free chloride content of BF-1 specimens was decreased by 17.8% compared to plain concrete (PC), and that of the specimens with 0.2% PAN fibers was decreased by 7.14%, while that of HF and BF-2 specimens exhibit the increase of 3.6% and 7.14%, respectively. When the fiber volume fraction is 0.2%, both are superior to ordinary concrete. Due to the positive hybrid effect of different fibers, the resistance to chloride ion penetration of HF is higher than that of BF-2. When the fiber volume fraction is 0.4%, the resistance to chloride ion penetration of fiber concrete (HF, BF-2) is worse than that of ordinary concrete due to the excessive fiber content. The surface chloride ion concentration and apparent chloride ion diffusion coefficient show obvious time-varying characteristics. The surface chloride ion concentration gradually increases with the extension of exposure time, and the apparent chloride ion diffusion coefficient gradually decreases. The power function and exponential function models can well predict the changes of the two. When conducting similarity analysis of different types of concrete, it is found that the acceleration effect and similarity of BF-2 concrete are the best, followed by HF concrete, and the BF-1 concrete with the best resistance to chloride ion penetration shows the lowest similarity and acceleration effect.