Abstract: Ermi Copper Deposit is controlled by Early Cretaceous Songdingshan volcanic organization.In order to achieve prospecting breakthroughs and instruct prospecting work,the paper analyzed the diagenesis and metallogenesis of the volcanic rocks inside the volcanic organization based on ore-forming geologic conditions,and came up with new understanding of prospecting direction.The study shows that the Songdingshan volcanic organization mainly includes 4 magmatic intrusions: diorite,quartz diorite,quartz monzodiorite and granite porphyry.The former 3 all develop main crater phase and parasitic crater phase while the granite porphyry closely related to copper mineralization only is detected with parasitic crater phase.Judging from the practical geologic data including the distribution range of the erupted materials in the same phase such as rhyolite,it is considered that it is likely that there develop concealed main crater phase granite porphyry rock mass inside the Songdingshan volcanic organization and the area should be considered as one of the major prospecting directions.