Australian coal was gasified in an internally circulating fluidized bed (0.3m ID X 2.7m high) with a draft tube (0.1m ID X 0.9m high) and a gas separator over the draft tube at atmospheric pressure. The effects of reaction temperature (780-900℃), oxygen/coal ratio (0.30-0.53), coal feeding rate (5.3-12.1kg/h) and steam/coal ratio (0.30-0.81) on compositions of the product gas, carbon conversion, cold-gas efficiency, gas yield and calorific value of the product gas have been determined. In the present coal gasifier, low calorific value gas (3.3-5.9MJ/㎥) in the draft tube region and medium calorific value gas(8.6-13.2MJ/㎥) in the annulus region can be obtained. A predictive mathematical model is proposed based on the bed hydrodynamics, reaction kinetics and the empirical correlation of pyrolysis yields to predict gasification characteristics in the internally circulating fluidized bed gasifer with a draft tube. The model including the effect of combustion reaction in the freeboard region can explain the reaction behavior more precisely than the model excluding the effect of combustion reaction in the freeboard region in the reactor within the range of variables studied.