NiFe2O4 nanoparticles with on average grain size of 12nm were compacted into nanosolids under the pressure of 0.0—4.5GPa.The M?ssbauer spectra of NiFe2O4 nanosolids at room temperature and low temperatures show that high pressure has a strong influence on the magnetic interaction and interface atomic state inside the nanosolid,though the crystal structure and average grain size of nanosolid do not change under high pressure.Under high pressure,the superparamagnetic relaxation of NiFe2O4 nanosolid is suppressed obviously by the enhancement of the interparticle magnetic dipole interaction and the superexchange interaction among the interface ions in the nanosolid,and the magnetic anisotropy of it is also weakened by the interparticle magnetic coupling in it.At the same time,the symmetry and the degree of short-range order of the polyhedrons are raised gradually with the increase of pressure,and then the atomic structure in the surface and interface zone of NiFe2O4 nanosolid shows a tendency to change into the grain boundary structure of common polycrystalline solid with large grain size.