Abstract: The time-averaged and root-mean-square fluctuation velocities of gas and particle phases and particle mass flux distributions have been measured by a 2-dimen-sional laser Doppler velocimeter combined with a sampling probe in a combustor of co-flow jets with large velocity difference. The results show large velocity slip between gas and particle phases. The gas-phase flow has astrong reverse flow in the near-axial region, while particles keep their forward motion almost everywhere, even in the strongly reverse flow region. The particle mass flux distributions measured have their maximum values in the near-axial reverse flow region. Presence of high-velocity jets remarkably enhances particle mixing. All these facts reveal the mechanism of flame stabilization and combustion intensification in the combustor of co-flow jets with large velocity difference. The four peaks of gas turbulence intensity observed in experiments demonstrate that the turbulence is caused by large velocity gradient resulted from sudden expansion and high velocity jets.Particle turbulence intensity has the similar behaviour as gas one,but the former is not always smaller than the latter. This means that the classical Hinze-Tchen's theory of particle following gas motion must be reexamined.