Abstract: This paper studies the ore-control factors of the Lantian uranium field,which is the firstunderground leaching exploitation in China. The main ore-control factors locating in the margin of fault basin include multiple magmatic activity,compound faults of NNE & NE and mass mafic dikes of the field. The mineralization process includes 5 stages. ① The formation of theγ₅2-2;②The preenrichment of U caused by the multiple magmatic activity;③ Alkali-alternation caused by mantle fluid activate the uranium of the accessory minerals,and the mantle fluid provide abundant ∑CO₂;④Uranium which is moved as UO₂(CO₃)O₃4-deposit in right physic-chemical circumstance and ⑤The phase of overprinting and reworked mineralization of oxidation and leaching.