The amount of oil and gas resources in the Mosuowan area of the Junggar Basin is substantial. However, the reservoir accumulation process of the Badaowan Formation and Sangonghe Formation is complex, while the timing and period of oil and gas accumulation require further study. Fluid inclusion analysis is a key method for this research. The density formula and isovolumetric method of PVT and NaCl-H2O solution inclusions were used to reconstruct the ancient formation pressures by observing conducting temperature, the petrographic characteristics of fluid inclusions and salinity measurements on 40 reservoir samples from the Sangonghe and Badaowan formations across 3 wells in the Mosuowan area.This data was then combined with burial history, thermal history, and hydrocarbon generation history to determine the oil and gas accumulation periods and to study the accumulation process. The results show that the accumulation period of the Sangonghe-Badaowan formations can be divided into two stages: crude oil filling, and condensate oil and gas filling followed by dry gas filling. The homogenization temperature range of inclusions during the crude oil filling period is 92.7–118.1 °C with paleopressures of 36.2–72.4 Mpa, corresponding to the end of the Early Cretaceous to the middle Paleogene. Corresponding to the late Cretaceous to late Neogene, The homogenization temperature range for the condensate oil and gas as well as dry gas filling period is 99.9–132.3 °C with the paleopressures of 56.2–118.2 Mpa. Paleo-overpressure is generally observed in the Sangonghe-Badaowan formations in the Mosuowan area. The primary cause of this overpressure is the hydrocarbon-generating pressurization from the Permian source rocks in the western depression of Well Pen-1 during the Middle and Late Jurassic, which transmits to the Mosuowan area. As dry gas and condensate oil and gas fill the formations, the contribution of hydrocarbon generation to the formation overpressure has gradually increased.