The chloride diffusion performance of basalt/polypropylene fiber reinforced concrete （BPFRC） was studied by using natural immersion method to simulate the marine underwater area. The chloride content in BPFRC under different exposure time was measured by solid-liquid extraction and potentiometric method， and the effects of fiber type， its content and hybrid form on chloride content profile， surface chloride content （C_s） and chloride diffusion coefficient were investigated. In addition， the pore size distribution of BPFRC was measured using Rapid Air 457， and the fractal dimension of pore structure was calculated. The results show that the chloride content in BPFRC increases with increasing exposure time. When the fiber volume fraction is 0.10%， the effect of basalt fiber on reducing chloride content in concrete is greater than that of polypropylene fiber， and an appropriate amount of hybrid fiber can reduce the chloride content in concrete. The excessive hybrid fiber increases the chloride content at different depths in concrete. The C_s of BPFRC increases gradually with increasing exposure time， and the relationship between C_s and exposure time is a power function. The pore structure of BPFRC shows obvious fractal characteristics， and the fractal dimension ranges from 2.301 to 2.446. The fractal dimension has a strong positive correlation with chloride diffusion coefficient.