Abstract: An internal recycle gradientless reactor had been designed for studying gas/solid catalytic reaction kinetics. The construction of the reactor is simple. The electromagnetic stirrer was employed in order to overcome the difficulties of the radial sealing of the rotating shaft. The catalyst may be put on the perforated fixed plate or in the rotating basket moving with the shaft. It enables to accommodate catalyst size from a few tenth of a milimeter to commercial size. Residence time distribution measurements showed that the gas flow pattern was ideal mixing flow. The axial and radial temperature differences in the reactor were very small. The reactor may be operated up to 800(C). The relation between residence time distribution and the stirring speed for various gas volumetric rate was studied. In order to reach perfect mixing state, higher stirring speed were required for higher gas flow rate. The re-actant concentrations in reactor effluent were measured under various stirring speed. The compositions were unchanged after the stirring speed had been increased to a certain value.