This paper analyzed the reason why heat-exchanger in central process factory of Songnan Gas-field is ineffective. It is mainly caused by the unqualified circulating cooling water quality, the impurity attached in heat transfer area.In addition, the scaling in internal wall of water pipeline reduces the real diameter of pipeline and the reduced flow caused inadequate water supply in high point and terminal heat-exchanger.Through analyzing of the water and scaling samples, the component of scaling samples mainly consist of some of mineral ions such as Ca2+、SO42-、CO32-etc.They are precipitated by a concentrated process of circulation and heat transfer in heat transfer area.The components of other materials are mainly clay which is produced by granular clay and microorganism.The leading causes of unqualified circulating cooling water quality are supplementary fresh water with sediment, the minerals precipitated by evaporation of circulating water, the failed bypass filter and circulating water without chemical agent.Following measures have been taken to effectively improve the quality of circulating as installing elementary filter in the outlet of water source well, the substitution of heavy concentrations water, the solution of blockage in recycling tank and the injection of chemical agents,which provides reference for improving circulating water quality in natural gas purification industry.