By the electrospinning and calcination techniques, we have prepared uniform nanofibers of Co1-x Zn (x) Fe2O4 (0.0a parts per thousand currency signxa parts per thousand currency sign0.5) ferrites with diameters of 110-130 nm. The Co1-x Zn (x) Fe2O4 nanofibers are single-phase spinels and the lattice constant with Zn content deviates from the Vegard's law for these Co1-x Zn (x) Fe2O4 nanofibers. The Co1-x Zn (x) Fe2O4 nanocrystal grains by which are built nanofibers increase with calcination temperature. Variations of coercivity and saturation magnetization with calcination temperature can be explained in terms of the grain-size (D) effect. The coercivity (H (c)) of Co0.5Zn0.5Fe2O4 nanofibers varies as D (0.65) and basically follows the predicted D (2/3) dependence based on the random anisotropy model in a D range below the single-domain size around 40 nm. The saturation magnetization of Co1-x Zn (x) Fe2O4 nanofibers initially increases with increasing Zn content, reaches a maximum value at x=0.3 and then decreases with further increase of Zn content, while the coercivity exhibits a continuous reduction with the increase of Zn content.