Abstract: Based on the facts that immature crude oils discovered at home and abroad are related to the environment of evaporates, ex. the oil in the 1st section of the Qianjiang Formation encountered by Huan No.33 well in the Changqing Oilfield, the Tertiary immature oil in Shiqma region of Isreal, etc. The origin of immature crude oils in evaporitic environment is studied in this paper. The author briefly introduces and reviews the following opinions on the origin of immature oil proposed recently. 1.strong reductive environ-ment is favourable for the preservation and the transformation of organic matter in early stage, and 2.the types of organic matter are the prerequisite of the formation of immature oils. Thereafter, it is suggested that the oil generated in evaporates may firstly migrate upwards and then changes into an immature oil, based on the study of the oil generated in the evaporitic sediments of the Gulf of Suez, Egypt.