Abstract: The flow pattern and transition law of gas-liquid two-phase flow in inclined rising pipe under different fluctuant nonlinear vibration conditions were studied experimentally. The flow patterns of gas-liquid two-phase flow under fluctuant nonlinear vibration condition were identified by using high-speed camera. The results show that there are four kinds of patterns in inclined rising pipe with diffuse bubble flow, fluctuant slug flow, proto slug flow and liquid-ring annular flow. The mechanisms of the transition from diffuse bubble flow to fluctuant slug flow, proto slug flow to liquid-ring annular flow were derived, the vibration parameter was added on the basis of the steady state transition mechanism and the flow pattern transition formulae considering the vibration acceleration were established. The results show that the flow pattern transition formulae established in this paper agree well with the experimental results.