Coke oven gas (COG) dome injection in COREX melter gasifier is recognized as one of effective method to reduce the amount of solid fuel used for gasification. In this work, a static model was developed to study the characteristics when COG is injected from dome. The critical bosh gas and critical fuel rate in COREX melter gasifier under different melting rate and coke rate were discussed. The amount of COG injection from dome under the critical fuel rates was studied. The results shows that when the heat of bosh gas reaching the critical value, the decrement of fuel rate decreases with the increase of melting rate and increases with the increase of coke rate. Under the critical fuel rate, the total volume of COG increases with the increase of melting rate and coke rate. After the COG injection, the amount and reduction capacity of the generator gas can meet the needs of reduction in shaft furnace. The findings of this work can be used as a theoretical basis to guide plant operations for COG injection.