The unsteady characteristics of heat transfer and particle behavior around a horizontal tube bundle near the expansion surface of a gas fluidized bed were experimentally studied. The instantaneous local heat transfer coefficient and the number of particles making contact with the heat transfer surface were measured simultaneously at the same location on the tube surface. The distributions of the local average heat transfer coefficient in the period during no particle contact were qualitatively similar to those for the gas single-phase flow, but were 2∼5 times larger than those for the corresponding gas single-phase flow. The relation between the local average heat transfer coefficient in the period during the particle contacts and the average number of the contacting particles were quantitatively evaluated.