In order to explore the effectiveness of electrical resistance tomography (ERT) technology in testing the concrete placement uniformity of large-diameter bored piles, numerical simulation was conducted to optimize the key parameters of ERT sensors. A physical model test was carried out using a sensor with a diameter of 1 000 mm as an example. The signal-to-noise ratio, sensitivity uniformity, and sensitivity matrix condition number, as well as the error, relative error and correlation coefficient of spatial images were used to evaluate the performance and effect of the sensor. The results show that the sensor height has a limited effect on the sensor performance, while the conductivity of electrode material has no impact on the sensor performance. There exists a complex nonlinear relationship between the electrode length, width, and sensor performance. When the height of ERT sensor is 0.8 times the diameter, the electrode is copper, and the length and width of the electrode are 1/16 and 1/32 of the circumference of the cylinder, respectively, the ERT sensor demonstrates good performance in testing the concrete placement uniformity of large-diameter bored piles.