Abstract: The theory of the large-scale mineraiization occurring in small intrusion is based on mineral exploration of magmatic sulfide deposit in China,and is an original principle of ore deposit.The key of this theory is similar to the formation of magmatic sulfide deposits in magma conduit system.In this paper,we attempt to summarize the general features and the key formation mechanism of the small intrusions of the magmatic sulfide deposits occurring on magmatic conduit system.We also try to estimate the prospecting direction and criteria of this type magmatic sulfide deposit.All of these are very significant to promote further researches and exploration of this type of deposit.