Intermediate to mafic dyke swarms were newly discovered in Urho area in the south of the Hala'alat Mountain which is located in the east of Western Junggar. The dyke swarms intruded into the Permian Jiamuhe molasse formation. The nearly NE-SW-trending dyke swarms are parallel to Darbut Fault. The rocks are mainly composed of diabase, diabase porphyrite and gabbro-diorite, which have features of low K calc-alkaline basalt to andesite series, as shown by geochemical analyses. The dyke swarms have low REE (34.53×10^-6～82.43×10^-6) and the anomalies of δEu (0.74～0.98) and δCe (0.98～1.15) are not obvious. REE distribution patterns are of the right-oblique type (LREE/HREE=2.47～7.18). All samples are characterized by the enrichment of LILEs (K, Rb, Ba, Sr) and depletion of HFSE (especially Nb, Ta), showing the characteristics of island-arc zone. Positive εNd(t) values (5.51～5.71) and relatively low initial Sr isotopic ratios (0.703 802～0.704 223) indicate the depleted mantle-related source. The source was the depleted mantle wedge and the magma was genetically influenced by the subduction components. The dyke swarms in Urho area suggest that the subduction between plates still went on after the completion of the compressional orogeny in early Permian. The lagged arc magmatism occurred later than the subduction in the west and middle of Western Junggar, suggesting that the final completion of the subduction in Western Junggar was in late Early Permian.