|Abstract:To find out the reason for hydrocarbon enrichment differences in Wenchang B sag, based on fault distribution and formation periods, structural styles and combination, the difference of tectonic evolution and fault activity, the different extension and strike-slip mechanism was built, identified that Sub-sag 19 was in extension and strong-strike-slip setting, Sub-sag 14 in extension and medium-strike-slip setting, and Sub-sag 30 in extension and medium-strike-slip setting. The different extension and strike-slip provided source channels and reformed reservoirs, also controlled the distribution and expelling direction of excellent source rocks, the carrier system types and migration dynamic, the trap types and mechanical property. Moreover, based on pre-existing fault form, dextral evolution of extensional stress field and strain difference, the recognition method of strike-slip stress-increased traps was built, divided in 3 type such as S-shaped stress-increased traps, dextral left-step stress-increased traps, and skew-shaped stress-increased traps. In conclusion, the hydrocarbon enrichment in Wenchang B sag was controlled by extension and strike-slip setting and source-migration configuration, Sub-sag 19 and 14 were hydrocarbon enrichment region owing to stong-medium strike-slip setting and excellent source rocks in semideep lacustrine facies. Finally, the study achievement had promoted several exploration discoveries in Wenchang sag.