The habitat preference and impact factors of population dynamics of hen harrier Circus cyaneus during four years observation in Shahu Nature Reserve in Hubei, China were analyzed. The results showed that there was no significant difference in ANOVA in the hen harrier′s yearly richness between different years. However, Independent Samples T Test of seasonal impacts indicated that there was a significant difference between autumn and winter of the four years, and that the abundance of autumn of hen harrier was higher than that of winter. Analyzing the abundance of hen harrier in ANOVA showed a significant difference among four habitats, with mean rank of grassland＞reed＞farmland＞water area. The rank of coefficients of variation of hen harrier abundance in the four habitats was grassland＜water area＜reed＜farmland. Moreover, analysis using Independent Samples of Nonparametric Tests (Kruskal-Wallis H) indicates that there was significant difference in the abundance of passerines and common pheasant Phasianus colchicus among the four habitats. The abundance of hen harrier was significantly correlated with that of prey in the reed and grassland, but weakly in the farmland and water area, exhibited in multiple linear regression models. Analyzing with dummy linear regression model further revealed that the abundance of hen harrier in grassland was associated with the following factors. The number of hen harrier in grassland declined significantly with the decrease of grassland proportion as shown by ANOVA. However, backfire of purse net to hen harrier of water area, and fish net setting around the lake had only minor impact on marsh harrier appearance in an Independent-Samples T Test. Taken together, these results indicated that grassland was the comparatively agreeable habitat for hen harrier to live through winter in the four habitats.