Electrical resistance tomography (ERT) and fiber optic were applied to investigate phase holdups and phase propagation velocities in a gas-liquid-solid circulating fluidized bed (GLSCFB). Since ERT is applicable only to conductive phase(s), e.g. the liquid phase in this study, a fiber optic probe was employed simultaneously to quantify all three phases. Saline water was used as the conductive and Continuous phase. Glass beads and lava rocks constitute the solid phase and air as the gas phase. Glass beads were transparent and spherical in shape: however. lava rock particles were irregular in shape and opaque, which affected the signals obtained from the optical fiber probe. An empirical model was developed to measure the gas holdup using optical fiber probe data. Gas holdup was higher in the central region and decreased radially, while opposite trend was observed with solid holdup due to the drag forces imposed on solid particles by the gas and liquid flow in the riser. By applying cross-correlation between the data obtained at two different levels ill the riser. nonconductive phase propagation velocity was obtained. The propagation velocity was higher in the central region compared to the wall region and increased with increasing liquid superficial velocity.