Lamei iron deposit in Central Yunnan is located in the middle section of the Jinshajiang-Ailaoshan- Honghe alkali-rich porphyry belt in the "Sanjiang" area of Southwest China. Its mineralization type is unknown and its metallogenic mechanism and resource potential are unclear, which restricts the in-depth study of prospecting and exploration in this area. On the basis of detailed geological survey, and according to the output characteristics of the ore bodies, magnetite is divided into three types: bean-star point magnetite in syenite porphyry(Ⅰ-Mag), disseminated-agglomerate magnetite in diopside hornstone(Ⅱ-Mag) and vein-shaped and sac-like filling magnetite in interlayer fracture zone(Ⅲ-Mag). Through LA-ICP-MS in-situ micro-area composition comparison, it is found that the three types of magnetites are generally enriched in Ti, Mn, V, Mg, Zn and Ni, poor in Sn, Ga and Sc and other elements. Ⅰ-Mag→Ⅱ-Mag→Ⅲ-Mag, the content of Mg, V, Zn and the ratio of Ni/Cr gradually increase, and the content of Cr, Sn and REE gradually decrease, reflecting the evolution characteristics of the three types of magmatite from magmatic origin to hydrothermal origin. Combined with Ni/(Cr+Mn) -(Ti+V), (Al+Mn)-(Ti+V) diagrams and the ore facies characteristics of magnetite, the deposit is considered to be a contact metasomatic hydrothermal iron deposit, and its mineralization material source is closely related to alkali-rich porphyry. The formation temperature of three types of magnetite is about 300~500℃, and the oxygen fugacity of Ⅰ-Mag→Ⅱ-Mag→Ⅲ-Mag tends to decrease gradually. Geochemical characteristics, mineralization temperature, oxygen fugacity and other information indicate that the deep part of Lamei iron deposit has the metallogenic potential of a porphyry copper polymetallic deposit.