Electrical capacitance tomography (ECT) has been widely used in fluidized bed measurements because of the noninvasive and nonintrusive features. The successful application of ECT in fluidized bed measurements depends on the appropriate design of sensors. This paper discusses the effect of ECT sensor length on fluidized bed measurements by simulations and experiments. The sensitivity distributions in different axial positions of a sensor are compared, which shows the similarity of sensitivity distribution contours and decline of intensity along the sensor axial direction. Fluidized beds of three different diameters (45, 55, and 65 mm) are used to compare the effect of sensor electrode length on fluidized bed measurements. In each fluidized bed, five sensors with different electrode lengths are tested. The experimental results show that the sensor electrode length has significant effect on bubble detection in fluidized bed measurements, and it is recommended that the sensor electrode length should be as short as possible considering the signal-to-noise ratio constraint.