In this work, gas phase distribution characteristic and separation performance of a new vane-type gas-liquid separator were carefully investigated using electrical resistance tomography and numerical simulation. The diameter of the separator was 100 mm and the flow rate ranges from 12.0 to 23.0 m3/h. The gas flow rate ranges from 1.2 to 4.0 m3/h. In the experiment, electrical resistance tomography was applied to test section void fraction distribution. Coriolis mass flow meter was applied to obtain separation efficiency by testing separator exits mixture density. In the numerical simulation, full Eulerian multiphase model, together with RNG k-ε turbulent model and dispersed phase zero equation models were applied. Results show that the vane-type gas-liquid separator's performance is influenced by gas core size. The separator performs well in all the cases, considering separation efficiency is over 85%, and achieves nearly 100% through adjustment of split ratio. All these findings are beneficial for vane-type gas-liquid separator design and optimization.