A magnetic detection circuit for a magnetic random access memory (MRAM) is provided. The magnetic detection circuit includes a sensing array including a plurality of sensing cells and a controller. Each of the sensing cells includes a first magnetic tunnel junction (MTJ) device. The controller is configured to access the first MRAM cells to detect the external magnetic field strength of the MRAM. The controller determines whether to stop the write operation of a plurality of memory cells of the MRAM according to the external magnetic field strength of the MRAM, and each of the memory cells includes a second MTJ device. The first MTJ device is smaller than the second MTJ device.