The invention provides a downhole vertical magnetic probe, which comprises a pole plate assembly and two main transmitting coils. The two transmitting coils are winded in differential manner, a pair of auxiliary magnetic coils are provided in the two main transmitting coils, a shielding layer is provided outside the two main transmitting coils, the pole plate is composed of eight pole plates, each pole plate has eight receiving coils, and the 64 receiving coils in total are staggeredly arranged in array manner; and a signal amplifier is provided in the pole plate. The invention can accuratelyidentify the damaged condition (by wall thickness) at any positions of the downhole sleeve wall, overcomes the measurement error caused by the existing electromagnetic eddy current thickness meter, effectively improves measurement accuracy, and is an ideal probe in electromagnetic eddy current filed.