The invention relates to a hydrogenation process for preparing oil products from coal tar which is generated together with exhaust gas synthesized during preparation of methanol from a coke oven and coal gas. Methanol is prepared from coal gas which is the by-product of the coke oven, large amount of relief gas and nitrogen gas during the methanol preparation process, hydrogen is extracted from the relief gas and used as one of the materials for hydrogenation preparing light fule oil from tar, nitrogen is extracted as the material of a coke dry quenching unit, the heat energy generated during the coke dry quenching process is used for generating electric power. With the recycling of coke oven coal gas, the prior exhaust gas which is directly exhausted or burnt is changed into a high-value product, such as electricity, methanol, light fuel oil, advanced charcoal material, etc., at the same time, the object of energy conservation can be realized.