Abstract: In a method for measuring brain free water content, in response to an RF excitation field generated on the basis of a magnetic resonance fingerprinting sequence and applied to the brain, an equilibrium magnetization mixed term (M0) signal is acquired from radiation emitted by each excited voxel of the brain, to obtain an M0 value of each voxel of the brain; a receive coil sensitivity (RP) value of each voxel of the brain is acquired; the M0 value of each voxel of the brain is divided by the RP value of the corresponding voxel to obtain a proton density (PD) value of each voxel of the brain; a PD value of cerebrospinal fluid is taken to be a reference PD value; and the PD value of each voxel of the brain is divided by the reference PD value to obtain the free water content of each voxel of the brain. The method advantageously increases the speed and accuracy of measurement of brain free water content.