The different extension and strike- slip mechanism was built to understand the mechanisms responsible for differences in hydrocarbon enrichment in Wenchang B sag, based on fault distribution and formation periods, structural styles and combination, the difference in tectonic evolution and fault activity. The results indicate that the 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 not only provided source channels and reformed reservoirs but also controlled the distribution and expelling direction of source rocks, the carrier system types and migration dynamic, the trap types and mechanical properties. Moreover, based on the pre- existing fault form, dextral evolution of extensional stress field and strain difference, a recognition method of strike- slip stress- increased traps was built and divided into 3 types: 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 the extension and strike- slip setting and source- migration configuration, Sub- sag 19 and 14 were hydrocarbon enrichment region owing to strong- medium strike- slip setting and excellent source rocks in semi- deep lacustrine facies. Finally, the study has promoted several exploration discoveries in the Wenchang sag.