Abstract: Effects of the pyrolysis chamber on the pressure distribution and the behavior of gas/solid flow in the standpipe of a CFB combined with coal pyrolysis reactor were studied. The riser column was 0.1m in diameter, 6m in height. And the standpipe was 0.044m in diameter, 3m in height. The rectangle pyrolysis chamber with cone-shaped distributing plates laid between the cyclone dipleg and the standpipe. The across section and the height of the chamber are 200mm×200mm and 0.77m respectively. The experiments showed that with the increase of the superficial gas velocity in the riser, Ur , the flow pattern in the standpipe was negative pressure difference flow whether the pyrolysis chamber was set up in the standpipe or not. And the negative pressure gradient decreased with Ur increasing. Solids in pyrolysis chamber must maintain a certain height, the flow pattern in the whole standpipe was negative pressure difference moving bed. If without pyrolysis chamber, the lean phase flow and the moving bed flow co-existed in the standpipe. And with the increase of Ur ,the equilibrium height of the solid in the standpipe was heightened. With circulating rate Gs increasing,the negative pressure gradient in the two type standpipes increased also. Without pyrolysis chamber, the increase of the circulating rate Gs would cause the equilibrium height of the solid in the standpipe declined. With Gs increasing the slip velocity in the standpipe was also increased.