The Caosiyao molybdenum deposit in Xinghe County, Inner Mongolia is a super-huge type deposit. Through the analysis on the geochemical characteristics of the deposit, the authors think that the debris geochemical measurement is a effective method to find porphyry molybdenum ore. The main molybdenum body outcrops are strictly limited in the comprehensive abnormal center of the element Mo、W、Cu、Pb、Zn、As and Sb. The metallogenic parent rock, granite porphyry is not only the main ore-control factor but also the crucial ore-hunting indicator. Element combination classification and horizontal zoning characteristics indicate the direction of the orebody prospecting. Consequently the metallogenic geochemical model of the Caosiyao molybdenum deposit was established.