In order to investigate the fluctuation characteristics of two-phase flow splitting at a T-junction, particular attention was paid on Churn flow which had the strongest fluctuation comparing with bubble flow and annular flow. The main tube of the T-junction was vertical and the two branches were horizontal. All three pipes connecting to the junction were of 15 mm inner diameter. A statistical analysis based on Root Mean Square (RMS) was applied to temporal differential pressure signals and gas flow rate signals. The Power Spectral Density (PSD) was also employed to reveal their peculiar features in frequency domain as well. The effects of the extraction flow ratio and the gas and liquid superficial velocity upstream on fluctuation characteristics of gas-liquid two-phase flow splitting at the T-junction were investigated in detail. It is found that there is a wide fluctuation in both differential pressure and gas flow rate downstream at every extraction ratio (W-3/W-1) and the fluctuation intensity increases as W-3/W-1 increasing. It is also made clear that increasing either water superficial velocity or gas superficial velocity in inlet causes fluctuation to become more intensive. (C) 2002 Elsevier Science Ltd. All rights reserved.