Abstract On the basis of organic studies, this paper presents the geochemical characteristics of immature crude oil and source rock from the Anjihai Depression, Junggar Basin. The vitrinite reflectivities ( R °) of Tertiary rock samples are less than 0.6% at depths of 3000–4000 m. Sterane αααC 29 S/( R + S) values range between 0.049 and 0.23, and C 29ββ/(ββ + αα) values range from 0.30 to 0.48 in the Tertiary rock samples. The above two ratios of the crude oils are 0.44 and 0.47 respectively. Ratios of Σ rearranged steranes and Σ total steranes are in the range of 0.02–0.15 for both crude oil and Tertiary rock samples. These results show that the Tertiary rock samples are in a lower evolutionary stage, and crude oils originating from the Tertiary system are immature.