Abstract: A downhole electromagnetic logging tool comprises a transmitting system, a magnetic field sensor array and a control module. The transmitting system and the magnetic field sensor array are both connected to the control module. The transmitting system comprises an upper emission coil and a lower emission coil, which are respectively arranged above and below the magnetic field sensor array, for generating magnetic fields of opposite polarities, allowing the magnetic fields to be concentrated at the magnetic field sensor array. A casing generates a secondary magnetic field, which is received by the magnetic field sensor array to complete detection of the casing.