Abstract: Effects of exchange-coupling interaction between grains on the effective anisotropy in nano-composite permanent magnets were investigated, taking Nd₂Fe₁₄B/α-Fe as sample. The effective anisotropy of nanocomposite magnets can be calculated by the statistical mean values of the effective anisotropy between the magnetically hard-hard, hard-soft and soft-soft grains. The calculated results show that the effective anisotropy constant K_eff decrease with increasing magnetically soft phase component and enhance with increasing grains size ratio of soft phase to hard phase while the phase component fractions are fixed.