Abstract: There are high contents of naphthalene acids in the crude oils from Liaohe ,Shengli and Xinjiang oil fields.The diesel oils derived from these crude oils are highly acidic.In order to eliminate naphthalene acids in diesel oils,alkali washing processes have been developed. but emulsification is usually critical.The emulsification degree is affected strongly by the different diesel oil fed into the equipment,which results in unstable production.In this work,a demulsification process was developed for straight run diesel oil from Xinjiang crude oil,and some suitable demusifiers were chosen.Afterwards,the effects of demulsifiers in alkali washing of atmospheric triside cut diesel oils with different acidities were evaluated and the optimum amounts of alkali added were investigated.