Fractional domain magnetic resonance imaging method in uneven main magnetic field

The invention discloses a fractional domain magnetic resonance imaging method in an uneven main magnetic field, belonging to the field of magnetic resonance imaging (MRI). The method comprises the steps of measuring magnetic field intensity of a plurality of points on a certain surface of a to-be-imaged tissue, building an imaging area magnetic field intensity distribution model, then building a polynomial model of the magnetic field, and separating the polynomial model into a second-order polynomial model and a high-order polynomial model according to a measurement result whether the magneticfield has an obvious two-order component; substituting the two models into magnetic resonance FID signal, for the second-order model, resolving a spin density function of a certain layer of an imagedobject by using a fractional Fourier transform tool, for the high-order model, resolving an algebraic equation to obtain the spin density function of a certain layer of the imaged object, taking themodel and obtaining a grays