The coercive force of the domain-wall pinning model can be expressed as Hc=αpink2K1/μ0Ms-NeffMs. The dependences of the microstructure parameter αpink on the exchange and anisotropy constants of inhomogeneities are discussed in this paper. The results show that there is a wide range of the αpink values. The effects of magnetic parameter and thickness of Nd2Fe14B grain boundary on the αpink are also studied. It was found that αpink reaches the maximum where A′/A=0.5,K′1/K1=0.1 and the grain-boundary thickness r0=3.32nm. αpink of nanocomposite Nd2Fe14B/α-Fe magnets reaches the maximum when the grain size r0 is 7nm.