Abstract: Liquid slug length distributions of air/water slug flow in 50 mm i. d. horizontal pipe are investigated for a large range of gas and liquid superficial velocities. The results indicate that the distributions of liquid slug lengths can be well fitted by log-normal distributions, and the average liquid slug length have a typical function relationship of quadratic polynomial with the superficial mixture velocities of gas-liquid in a given liquid superficial velocity. When the liquid superficial velocity retains a lesser value, the Hurst exponent which reflects the long-distance correlation characteristic of the liquid slug lengths fluctuation has a linearly increasing relationship with the superficial mixture velocity. Then, the liquid slug length distributions obey the fractal statistics' law.