The Laoshankou granitoids located on the northern margin of the Junggar, Xinjiang, are composed of diorite, adamellite, syenite porphyry and diorite (porphyrite). Geochemical characteristics of biotite diorite and syenite porphyry show that the concentration of SiO2 of biotite diorite is from 54.43% to 55.10%, Al2O3 from 16.92% to 17.64% and CaO from 5.35% to 5.94%. They are high in total alkali (K2O + Na2O) content (9.00% to 9.43%) and enriched in potassic (K2O/Na2O= 1.32 to 1.74). Compared with biotite diorite, the syenite porphyry is high in the concentrations of SiO2 (59.96% to 63.60%), Al2O3 (18.15% to 19.13%) and Mg# (51.95 to 55.96), total alkali (K2O + Na2O=11.81% to 13.17%), and low in the concentrations of CaO（1.13% to 2.47%) and Mg# (30.16 to 48.20), K2O/Na2O ratio (1.1 to 1.53). They are belong to shoshonitic high K alkaline granitoids. In addition, they display noticeable enrichment on LREE, Rb, K, Pb, Sr and Zr, obvious depleted in Nb, Ta and Ti. These features, together with the regional geology characteristics, indicate that Laoshankou granitoids are formed under a subducted tectonic setting. The parental magma of syenite porphyry was residual melt left by clinopyroxene and amphibole fractional crystallization from biotite diorite parental magma derived from the mixed melt of riched potassium minerals mantle peridotites and subducted oceanic slab.