To study two-phase flow splitting at a T-junction, Parallel vertical riser pipelines were set up in the laboratory. Each of these pipelines was completely symmetrical. The experiment was conducted with various combinations of gas velocity and liquid velocities. Accurate measurement of gas-liquid two-phase flow were performed to determine whether the two-phase flow was evenly distributed in the two riser pipelines. The conductance probe technique was used to measure the average liquid holdup in the cross section of the pipe. Three flow patterns in two risers were observed during the experiment: slug-slug (S-S), churn-churn (C-C), and churn-slug/churn (C-SC). Gas-liquid flow of S-S and C-SC is asymmetric, while that in C-C is symmetric. When the flow state in the two risers is S-S, the gas-liquid two-phase split could be uneven. When the gas and liquid velocities were sufficiently high for sustaining C-C, the gas and liquid were split evenly. The last state was the transition state between S-S and C-SC. A model based on pressure-minimization was established to predict two-phase flow splitting. The measured and predicted flow splits were observed to be in agreement. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.