A downward gas-solid cyclone reactor (GSCR) was developed for conquering side reactions in fluid catalytic cracking technology. The ideal situation in the application of GSCR is that heavy gases are thrown to the vicinity of the outer wall and light phase products are pushed into the inner wall. Hence, the gradient distribution of particle concentration and gas products is beneficial to the cracking of heavy gases and the recovery of light gas products. In order to get insight into the flow pattern and microscopic characteristics of this gas-solid system, transient solid holdup at various axial and radial positions was measured by the PV-6. By adopting probability density function, power spectral density and cluster analysis, macroscopic and microscopic characteristics were analyzed and discussed. Experimental results show that an annular-core-annular structure exists in the diffusion chamber and agglomeration chamber. Solid holdup fluctuations near the outer wall of the diffusion chamber are severe. The probability is mainly distributed in low concentration band (epsilon(s) = 0.0-0.01), and the number of dense phases near the outer wall increases with the rising of particulate loading. The number of dominant frequencies decreases with the decline of particulate loading. Cluster analysis was carried out in the vicinity of the outer wall. The number of cluster group is higher while the duration time is lower in the agglomeration chamber. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.