Correct identification and chronology of intrusive and volcanic rocks is a prerequisite for understanding the succession of regional magmatic events and establishing chronostratigraphic framework. Aksu area, located in the Northwest Tarim block, is known for the successively exposed Neoproterozoic stratum and various kinds of igneous rocks and thus attracts many Precambrian researchers. This work reports typical intrusive characteristics among the basic rocks in the Sinian beds based on remote sensing image recognition, field profile geological survey and petrological study in the southwest Aksu city. These intrusive characteristics include truncating Sinian sandstone layers, wrapping wall rocks and fine- grained tendency of crystal size from the basic rock bed interior to margins. These typical intrusive features, integrated with our U- Pb chronological studies on zircons, indicate that the basic rock in the Sinian beds in the southwest Aksu area are not entirely Sinian erupted basalts- a part of them are actually Early Permian (ca.290 Ma) intrusive dolerite sills which was contemporaneous with the main eruption episode of massive flood basalt during the Permian Tarim Large Igneous Province. We suggest that they are an important component of the Tarim Large Igneous Province. This remarkable magmatic thermal event probably had a great impact on remagnetization of Precambrian rocks in this district. Meanwhile, it also highlights the importance of carefully recognizing and distinguishing the igneous rock types when conducting research on Precambrian magmatism in the Northwest Tarim block.