In order to predict the yield of coke oven gas (COG) when the blending ratio of semi-soft coking coal is high, we investigated the effects of coal properties on the yield and calorific value of COG. Semi-soft coking coals with high oxygen content generate COG with high concentration of CO and CO2 and low calorific value and the normalized COG yield (the normal gas volume yield of COG with the calorific value of 4800 kcal/Nm(3) per unit of coal mass) for these coals is low. Moreover, based on the fundamental experiment results at a laboratory scale, we developed two methods to predict the normalized COG yield. In one method, the normalized COG yield is expressed as a function of VM and oxygen content in coal, and in another method it is calculated by modified Dulong's formula, which is applied to estimate net calorific value of coal. The methods to predict normalized COG yield developed here proved being valid in the long-term industrial plant test. (C) 2016 Elsevier B.V. All rights reserved.