Abstract: The differential pressure signal of slug flow was gathered in a downward inclined pipe, and the time series of liquid slug length was obtained by utilizing the cross correlation analysis.The fluctuation characteristics of liquid slug length was discovered by using the statistics theory and fractal theory to analyze the time series of liquid slug length.The results showed that the effect of gas superficial velocity on liquid slug length was greater than the effect of liquid superficial velocity.When the liquid superficial velocity was relatively high, with increasing mixture velocity, the chaos of liquid slug length fluctuation would increase.When the liquid superficial velocity was relatively low, with increasing mixture velocity, the chaos of liquid slug length fluctuation would decrease.On the condition of a larger pipe inclination angle, the distribution of liquid slug lengths was more concentrated in a smaller range.The larger the inclination angle was, the better the long-range dependence of liquid slug length fluctuation was.