Abstract: The feasibility of gray water recycling system in iron and steel works and relevant evaluation indices were analyzed comprehensively. Then the evaluation indices of the system were given to evaluate the water-saving effects in the coking procedure of a certain iron and steel works quantitatively. The results showed that the water resource utilization efficiency as an index to evaluate the gray water recycling system is more reasonable and effective than those conventional indices as concentration multiple and recycling rate which are restrictive. For iron and steel works, the water resource utilization efficiency will increase 20, the quantity of industrial fresh water is decreased by 0.752 m³ per ton of coke and the annual quantity of industrial fresh water saved comes up to 5.34 million tons if the water reuse ratio is 0.5.