Abstract: The accurate identification of flow pattern is of great significance to improve the calculation accuracy of two-phase pressure drop. In this paper, the existing transition criteria of slug flow to churn flow were verified and evaluated using the static experimental data. On this basis, the best transition criterion was selected and the transition criterion between slug flow and churn flow under rolling condition was constructed by introducing the transient external force field produced by rolling motion, which was verified by the experimental data. The transition criterion was analyzed. The results show that with the increase of rolling amplitude, the transition of slug flow to churn flow advances a little, while the influence of rolling period on transition boundary can be ignored.