The magnetic steel is one of the commonly used components in a steel pipeline corrosion defect and deformation magnetic flux leakage detection magnetizing system, and the space magnetic field distribution is important for magnetizing effect and magnetic flux leakage detection precision. A novel automatic measuring device is designed for measuring the space magnetic field of the cylindrical magnetic steel, the detection device consists of a measuring table, a lifting table, a mounting base, eight linear feeding mechanisms used for adjusting the measuring positions of the magnetic field sensor are evenly arranged on the magnetic steel magnetic field measuring table, the mechanism includes a stepping motor, a lead screw sliding block, a guide light bar, a magnetic field sensor propelling rod,and magnetic field intensity distribution measurement of different positions of the same section of the magnetic steel is realized; the vertical lifting mechanism of the magnetic steel is composed ofa servo air cylinder, a lifting rod, a connecting rod and a sliding block, and through the combination with the linear feeding mechanism of the measurement position of the magnetic field sensor, themagnetic field intensity of different sections in the height direction of the magnetic steel can be measured, and therefore the drawing of the magnetic field intensity distribution of the space aroundthe magnetic steel is realized.