The roots of plants have the function of water absorption and transport, and some of them also have important medical value. The anatomical characteristics of coarse roots of 40 medicinal herbs were observed, the differences among functional groups were compared, the correlations of traits were analyzed, and the interspecific variability of root traits was explained in combination with phylogenetic and natural climate factors. The results showed that the root anatomical characteristics of herbaceous plants were significantly different among species. Compared with dicotyledonous plants, the proportion of root cortex in monocotyledonous plants was higher, while the proportion of median column was smaller, which revealed the differences in root absorption and transport strategies between the two plants. Traits network analysis showed that xylem area ratio (XAR) was the central trait with the highest degree and tightness. XAR was positively correlated with phloem area ratio but negatively correlated with cortex fraction (CF). Except for vessel frequency and CF, other traits showed no significant phylogenetic signals, indicating that root characters were less affected by phylogeny. In monocotyledon herbaceous species, mean annual precipitation was positively correlated with CF, while in dicotyledon herbaceous species, mean annual temperature was positively correlated with average vessel diameter. These would further reveal the diversity and adaptability of the root structure of medicinal herbs.