Abstract: Under nonlinear oscillation caused by seism, two-phase flow will affect loop heat transfer and impact reactor structure, so it is meaningful to study the gas-liquid interface behavior under seismic nonlinear oscillation. According to the method of combining vibration apparatus with two-phase flow experiment loop, the experimental study on gas-liquid two-phase flow in horizontal channel under nonlinear oscillation was conducted. At the same time, based on FLUENT platform, combined with dynamic mesh technique and UDF programming method, the mathematical model was established and verified. The results show that the simulation and experiment results are in reasonable agreement. The flow patterns of gas-liquid two-phase flow under nonlinear oscillation are different from those under steady condition, resulting in more complex gas-liquid interface, and main flow patterns are bead flow, fluctuant slug flow, boiling wave flow, wave flow and annular flow. As vibration intensifying, the magnitude of frictional pressure drop increases, showing vibration frequency has a stronger effect on fluctuation than vibration amplitude.