Abstract—In this paper,a systemthat canproducealterableand rotary permanent magnetic field is developed. It can be used for crystal growth, chemical crystal and biologic cell, etc. A homogeneous magnetic field can be produced in the central region by two annular permanent magnets, and the density of magnetic flux is controlledbychangingtheangleofthemagneticfieldproducedby the inner annular magnet and that produced by the outer annular magnet.Theanglecanvarycontinuouslyfrom0to180degree,consequently,causingthedensityofmagneticfluxvariedfrom0.006to 0.18Tesla.Toobtainarotarymagneticfield,thetwoannularmagnetsaredriventorotatesynchronously.Afterthewantedmagnetic fieldisachieved,therelativepositionoftheinnerandtheouterannular magnet is fixed, thus, the inner and outer annular magnets can rotate synchronously at a given speed. The rotation speed up to 20 rad/min can be achieved. A monitoring system, based on industrialcomputer,isusedtosetparameterstocontrolthemagnetic fieldandtherotationspeed,andtoshowthereal-timeoperationparameters andworkingstatusof the system.Throughexperimental verification,the measured data has good agreement with the given value. The system is also applied on a furnace for single crystal growth,theresultshownthatthequalityofthesinglecrystalbeing grown under magnetic field is significantly improved when compared to those grown under no magnetic field