The primary task of research into oil and gas exploration and accumulation mechanisms is to recover the thermal evolution history of source rocks, which has a significant impact on the evaluation of regional petroleum resources. This study aims to understand the characteristics of the thermal evolution history of the Jixian System source rocks in the Tongcheng- Ankou area of the southwest margin of the Ordos basin since the Mesozoic, and whether they were affected by the Early Cretaceous magmatic activity and to what extent. These questions restrict the understanding of the hydrocarbon generation potential and the hydrocarbon formation period of the Middle Palaeozoic source rocks of the southwestern Ordos basin. Apatite fission track, apatite/zircon (U- Th)/He of the Triassic System, the Jurassic System and the Tongcheng rocks exposed in the Ankou- Tongcheng area, as well as vitrinite reflectance data, were used to restore the tectonothermal evolutionary history of the sedimentary rocks since the Middle Triassic and the intrusive rocks since the Early Cretaceous in this area. Since the Mesozoic, the Jixian System source rocks have experienced a normal burial temperature increase from the Triassic to the Jurassic, reaching the hydrocarbon generation temperature threshold. They began cooling from 130~110 Ma in the Early Cretaceous. Modeling results showed a slight acceleration in cooling from the Mid- Eocene to ~45 Ma and rapid cooling from the Late Miocene to ~8 Ma. The study reveals that the Middle- Late Jurassic was the key period of hydrocarbon generation for the Jixian System in the southwest margin of the Ordos basin, and the hydrocarbon source rocks were in the main oil- generating temperature range. The thermal effect of the Late Early Cretaceous magmatic intrusion event was limited in scope, and its influence on the paleogeothermal temperature of the Jixian System source rocks only occurred locally. The Jixian System in the Middle Palaeozoic has some hydrocarbon generation potential in vast areas that were not affected by the Late Early Cretaceous magmatic thermal event, such as the Ankou area on the southwest margin of the Ordos basin which merit further research.