CN; mso-bidi-language: AR-SA" lang=EN-US>Middle Jurassic is the main layer system of hydrocarbon source rocks which develops widely in the Delingha depression. Field geological survey and organic geochemical analysis indicate that Middle Jurassic source rocks mainly include oil shale, mudstone, carbonaceous mudstone and coal. The oil shale is a good hydrocarbon-generating rock. Whose mass fraction of organic carbon averages 7. 95% and the type of organic matter isⅠandⅡ. Mudstone has different organic matter abundances, but over 80% samples whose mass fraction of organic carbon is more than 1% and over 65% samples whose mass fraction of organic carbon is more than 1. 5%. The composition and the distribution of hydrocarbon compounds indicate that Middle Jurassic belongs to a fresh water deposit environment, and there develops semi-deep lake facies and deep lake facies which are good depositional settings to deploy source rocks in the Delingha depression.