The invention relates to a method and device for preparing a silicon steel sheet in a static magnetic field with a powder sintering method. The specific process of the method consists of the following steps of: mixing Fe-Si powder; rolling into a plate blank; and sintering a Fe-6.5 weight percent Si green compact in a static magnetic field. In the method, 6.5 percent by weight of Si high-silicon steel with high density is obtained by using the influence of the magnetic field on the sintering densification and orientation process of a Fe-6.5 weight percent Si powder green compact, and an easily-magnetized axis is oriented along the magnetic field. An atmosphere/vacuum sintering device in a static magnetic field consists of a temperature control device, an exhaust pipe, a thermocouple, a heating element, a corundum crucible, a refractory fiber, a support block, a heat insulating block, a water-cooled bush, a static magnetic field generating device, a sealed corundum pipe, an inert gas inlet valve, a vacuum pumping valve, a Fe-6.5weight percent Si green compact, a thin corundum plate interlayer and a fixing molybdenum wire. The 6.5 percent Si silicon steel sheet prepared with the method has the advantages of near net molding, superior magnetic property, high orientation degree and the like, and has a remarkable industrial application prospect.