Trace elements are sensitive to the evolutionof sedimentary background during deposition, makingtheir content and ratios useful indicators of the tectonic background of sediment provenance, sedimentary environment and the paleoclimate.Based on the measurements of trace and rare earth elements from 23 mudstone samples and the sedimentary studies on cores and thin- sections, this paper carried out the reconstruction of paleosedimentary environment of the Paleogene Anjihaihe Formation in the Northwestern Junggar Basin.The study shows that: (1) REE/Chondrite patterns, upper mantle normalized trace element spider diagrams and the discrimination diagrams of Th/Sc- Zr/Sc, La/Yb- REE, La- Th- Sc and so on suggest development of astable sedimentsupply during the Anjihaihe Formation period. The provenance studies indicated a strong weathering process butweaker recycling and sorting. Sediments originated from felsic rocks from upper crust, andacid igneous rocks formed in continental island arc were the main type of parent rocks. The early Carboniferous intrusive rocks in Zaire Mountain are considered to be the most probable provenance. (2) During the Anjihaihe Formation period,the characteristics of element combinations such as Li, Sr, Sr/Ba, Th/U and U/Th, δ U, δ Ce,Ceanom, Ce/Laindicate that the study area developed in continental brackish water with an oxidizing environment. This environment was potentially influenced by a series ofwarm climate events in Paleogene when strong evaporation resulted in falling lake level. As a result, the salinity of water increased and some of bottom sediments were oxidized by subaerialexposure, forming continental red beddeposits. (3) From the bottom to the top of the Anjihaihe Formation,the evolution of Sr/Cu, Cu and Csrises, illustrating worsening drought. At the same time, there is a decrease in Rb/Cs showing a weakening weathering process. In conclusion, the Paleogene Anjihaihe Formation period experienceda process of climate change from damp- heat to dry- heat in the Northwestern Junggar Basin.