The drought-resistant shrubs Caragana korshinskii, Caragana stenophylla, Caragana roborovskyi, and Caragana tibetica, are distributed mainly in the arid and semi-arid areas of the Inner Mongolia Plateau, China. They are important plants for fodder resource, and are known as "lifesaving plants" to livestock. In addition, they play an important role in fixing sand dunes and conserving water resources. So far, however, very little attention has been paid to the factors determining the sand-fixing capability of Caragana shrubs. In this study, we explored the relationships between the morphology of shrubs and nabkhas and sand-fixing capability for the four dominant Caragana species in the desert region of the Inner Mongolia Plateau. The results showed that C. korshinskii nabkhas were spherical and coronary, C. stenophylla nabkhas were conical, and the nabkhas of C. roborovskyi and C. tibetica were platform and hemispherical, respectively. Within each of the four Caragana species, shrub aboveground biomass significantly correlated with both nabkhas' horizontal scale and slope angle (P<0.05), but not significantly correlated with nabkhas' vertical scale (P>0.05). Nabkhas' vertical scale significantly correlated with plant height (P<0.05). The correlation between nabkhas' horizontal scale and vertical scale was significant. The nabkhas' horizontal scale, vertical scale, and volume all increased with Caragana shrub's extension. And the development of shrubs and nabkhas was faster in horizontal scale than in vertical scale. The sand-fixing capability of nabkhas also increased as Caragana shrub extended. Among the four Caragana species, the morphological characteristics of shrub and nabkha were significantly different. C. korshinskii had the highest shrub height, the largest nabkhas vertical scale and the highest shrub aboveground biomass. C. roborovskyi had the largest nabkha horizontal scale, the smallest vertical scale, and the smallest slope angle. C. stenophylla and C. tibetica had relatively smaller nabkhas, but larger nabkha slope angles than the two Caragana species above. For C. korshinskii and C. stenophylla, the ratio between horizontal and vertical expansion remained relatively constant. But for C. roborovskyi and C. tibetica, the shrub height remained similar regardless of the size of shrub bottom. As the shrub extended, the nabkhas' bottom area of the four Caragana species all increased but with significantly different rates. The bottom area of C. roborovskyi and C. tibetica nabkhas tended to expand faster than that of C. korshinskii and C. stenophylla. Within the four Caragana species, the vertical expansion of C. roborovskyi was the slowest, resulting in the lowest plant height. While, C. korshinkii, C. stenophylla, and C. tibetica shrub nabkhas remained in relative balance in horizontal and vertical development. The order of nabkha volume and sand-fixing efficiency of four dominant Caragana species were all as following: C. roborovskyi > C. korshinskii > C. stenophylla > C. tibetica. Based on the results of this study, we can draw two main conclusions: (1) Within each of the four Caragana species, the nabkha volume, morphology and sand-fixing capacity were probably determined by shrubs' aboveground biomass. (2) Among the four Caragana species, the difference of nabkha morphology, development characteristics, and shrubs' sand-fixing capability were probably caused by the interspecific differences in morphology and development strategies.