Mud logging, well logging and formation testing data are used to set up equations for oil, water and dry layers identification of Putaohua reservoir in Ao 21 block of Aonan oilfield. In this paper, 10 variables are considered, 4 variables are selected into the functions. The oil, oil-water, water and dry layers identification in the studied area with discriminant functions is proved to be very effective with a precision of more than 80%.