The effects of exchange-coupling interactions between grains on the effective anisotropy and the variation in Nd2Fe14B/α-Fe nanocomposite permanent materials were investigated. The calculatied results showed that due to the exchange-coupling interactions, the effective anisotropy Keffof the nanocomposite decreases with the decrease of grain size and the increase of magnetically soft phase component. When the average grain size decreases to 4nm, Keff decreases to about 1/3—1/4 of the value of the ordinary anisotropy constant. This variation character is basically similar to that of the coercivity. The decrease of coercivity for the nanocomposite permanent materials is mainly due to the decrease of the effective anisotropy.