Electrical resistance tomography (ERT) is a new technique developed in recent years, which aims to measure multi-phase flow. The conductivity distribution images of cross section can be obtained, and then the gas holdup can be calculated using ERT system. Combining ERT technique and cross correlation measurement method, the velocity can be calculated. In this paper, the dual-plane digital ERT system was designed, and experiments were carried out on a small-scale gas/water two-phase flow experimental set-up. The on-line reconstructed images, gas holdup estimations and correlation velocity can be obtained. Experimental results showed that the reconstructed images with high spatial resolution and real-time performance can be obtained. The software has rich functions and user-friendly interface, which can meet the needs of visualized measurement for two-phase flow in practical application.