The traditional method of using three-phase alternating current to generate rotating magnetic field in teaching and demonstration instruments has many problems，such as high loss of instruments，potential safety hazards and high cost．A kind of frequency adjustable rotating magnetic field generation device is designed．Low voltage direct current is fed into the four radial horizontal solenoids with iron core，and the current reversal is controlled by programming the PLC board．At the same time，alter the reversal time can make the deflection cycle of the small magnetic needle placed in the center of the device change，so as to achieve the effect of frequency modulation． When single-phase constant direct current is passed through the solenoid，the small magnetic needle does not rotate;when the biphasic rectangular pulse current is passed through，the small magnetic needle rotates 45° per each step．The rotation speed of magnetic field depends on the frequency of current commutation．The device not only avoids the shortcomings of traditional methods，but also has functions of both qualitative demonstration and quantitative measurement．It can be used as an experimental teaching instrument with excellent performance．