There remains controversy about petrogenesis and tectonic environments of the Permian magmatic rocks in the southern margin of the Central Asia Orogenic Belt (CAOB). This study carried out analyses of petrology, zircon UPb isotopic geochronology and geochemistry of the Yiheshaorong complex massif in the Hanwula area of Xiwu Banner, Inner Mongolia. The results show that the Yiheshaorong complex massif comprises gabbro, pyroxene diorite and alkalifeldspar granite. Their geochemical features show SiO2 content of 4401%~7760%，which exhibits a gap between 5591% and 7597%, displaying a good bimodal geochemical distribution. LAICPMS UPb dating yielded the ages of 2801±13 Ma and 2798±12 Ma for gabbro and alkalifeldspar granite, respectively, suggesting they are early Permian intrusive rocks．The gabbros are a suite of lowK tholeiiticcalc alkaline rocks, with SiO2=4401%~5263%, Na2O+K2O=278%~533% (Na2O>K2O), Al2O3=1511%~2443%, TiO2=055%~359% and Mg#=23~60. Low total REEs and flat REE distribution pattern, positive Eu anomalies, enrichment of LILE (such as Ba, K, Sr, and Eu), and depletion of HFSE (like Nb, Zr, and Hf) imply that this gabbros were formed in a subduction setting. The alkalifeldspar granites are characterized by high SiO2，K2O+Na2O，FeOT/MgO，low Al2O3，CaO and MgO; relatively low total REEs and seagulltype distribution pattern; high total amount of trace elements, characterized evidently by enrichment of LILE (such as K, Th, U and Rb，and depletion of Ba, Nb, Ta, Sr, P and Ti). All these features are consistent with features of Atype granite. Therefore, the granites should be the product of partial melting of felsic crust in low pressure, high temperature condition. Together with their petrological and geological features，it can be concluded that the Yiheshaorong complex massif was most probably formed in a backarc spreading basin triggered by oceanic crust subduction before closure of the Paleoasian Ocean in the Early Permian.