A newly configured siphon, called the reactor siphon, was proposed to fulfill chemical reactions along with its control of the particle circulation rate in a circulating fluidized bed (CFB) mounted with the siphon. The new siphon has two separated seals to prevent bypassing of gases both from the riser to the downcomer and from the downcomer to the riser. This in turn allowed a reaction space, called the reactor of the siphon, to be created between the two seals independently of the riser and downcomer. In a CFB installed with a reactor siphon, the present article further investigated the ways to control the particle circulation rate of the bed. It was found that the pressure difference between the reactor of the siphon and the riser influenced greatly the particle circulation rate. This rendered the circulation rate little varied with the particle amount loaded into the whole bed when the pressure difference was substantially high. Changing the superficial gas velocity in the riser obviously varied the circulation rate, but this gas velocity effect was related to the quoted pressure difference as well. Consequently, the particle circulation rate in the CFBs mounted with the reactor siphon was thought to be subject to the dominance of both the gas velocity in the riser and the pressure difference between the reactor of the siphon and the riser, revealing essentially a controlling mechanism that is much different from that for the CFBs installed with the conventionally configured siphons.