In this paper, an industrial hot experiment was done for studying the flow structure and combustion characteristic of a 65 t/h oil-shale-fired circulating fluidized bed (CFB) dense phase. The operational characteristics of this boiler and the particle properties of crushed oil shale and circulating ash were obtained. The particle-size distribution and carbon content of solid particles within the dense phase were investigated along the horizontal direction under different boiler loads. The experimental results may be used as a reference for modeling the flow structure, combustion, heat transfer, and abrasion of the oil-shale-fired CFB dense phase. At the same time, the experimental data obtained lay a foundation for the scale-up of oil-shale-fired CFB boilers.