To study the influence of fiber on the water stability of asphalt mixtures, the optimum dosage of asphalt and fibers are studied by the method of Marshall test and rut test. The results demonstrate that the optimum dosage of asphalt and fibers are 4.63% and 0.30%, respectively. Then the improved effects of basalt fiber on water stability of asphalt mixtures are evaluated through immersed Marshall test and freeze-thaw splitting test according to related specifications. The results show that the freeze-thaw splitting strength and splitting strength without freeze-thaw of fiber-reinforced asphalt mixture are improved to some extent compared with control mixture. Splitting strength without freeze-thaw of basalt, polyester and xylogen fiber-reinforced asphalt mixture is increased by 36.4%, 15.4% and 6.2%, and freeze-thaw splitting strength is increased by 55.2%, 28.7% and 14.5%. It can be concluded that fiber can remarkably improved the water stability of asphalt mixtures, besides; the improvement effects of basalt fiber are superior to polyester fiber and xylogen fiber.