How to resolve contradictions between the nanoscale size and high saturation magnetization (Ms) remains one of the scientific challenges in nanoscale magnetism as the theoretical optimal Ms of nanocrystals is compromised by the surface spin disorder. Here, we proposed a novel nanotechnology solution, heterointerface constructions of exchange-coupling core-shell nanocrystals, to rearrange the surface spin for the enhancement of Ms of nanomagnetic materials. As a demonstration of this principle, single-interface coupling FePt@Fe3-δO4 core/shell nanocrystals and multi-interface coupling FePt@Fe3-δO4@MFe2O4 (M = Mn or Co) core/shell/shell nanocrystals were synthesized. The simulated and experimental results demonstrated that constructing coupling heterointerfaces orientates the overall magnetic moment, ultimately enhancing the Ms of nanomagnetic materials. Moreover, this work first demonstrated that the origin of coupling heterointerfaces arose from mismatched lattices rather than chemical composition mismatch at the core-shell interfaces, thus providing both a solution to unite different mechanisms and an explanation to explain the exchange coupling at heterointerfaces.