Two-interconnected fluidized bed systems are widely used in various processes such as Fisher-Tropsch, hot gas desulfurization, CO2 capture-regeneration with dry sorbent, chemical-looping combustion, sorption-enhanced steam methane reforming, chemical-looping hydrogen generation system, and so on. However, conventional two-interconnected fluidized bed systems are very complex, large, and difficult to operate because most of these systems require a riser and/or pneumatic transport line for solid conveying and loopseals or seal-pots for gas sealing, recirculation of solids to the riser, and maintaining of pressure balance. To solve these problems, a novel two-interconnected fluidized bed system has been developed. This system has two bubbling beds, solid injection nozzles, solid conveying lines, and downcomers. In this study, the effects of operating variables on solid circulation rate and gas leakage between two beds have been investigated in a cold mode two-interconnected fluidized bed system. The solid circulation rate increased as the hole diameter on the injection nozzle, the diameter of the injection nozzle, the solid height above the holes, and the number of holes on the injection nozzle increased. The gas leakage between the beds was negligible. Moreover, long-term operation of continuous solid circulation up to 60 hours was performed to check the feasibility of stable operation. The pressure drop profiles in the system loop were maintained steadily and solid circulation was smooth and stable.