Bryophyte is one of the main plant groups on karst rocky desertification slopes along mountainous roads. However, the effects of bryophyte on water retention and heavy metals’ enrichment are rarely known. Bryophyte samples and their substrates were selected from the rocky desertification slope along Provincial Guizhou305 Road to study the function of soil and water conservation of bryophyte and their adsorptive ability to heavy metal elements (Pb, Zn and Cd) from atmosphere. The results showed that 33 species belonging to 12 genera and 5 families were reported in the study area. The dominant species were Bryum argenteum, Didymodon fallax, Anombryum gemmigerum, Oxystegus cuspidatus and Weissia edentula. Relative abundance of bryophytes in the rocky desertification slope was negatively related to the rocky desertification area. The average rate of bryophyte’ saturated water absorption was from 849% to 1474%, and the average rate of pedogenesis was from 464% to 1025%. The saturated water absorption quantity was from 4.56×10⁴ to 2.63×10⁵ kg·hm^-2, and the pedogenesis quantity was from 4.01×10⁴ to 2.45×10⁵ kg·hm^-2. The concentrations of Pb, Zn and Cd in bryophytes were 2.25, 3.98 and 2.49 times as high as in their substrates, respectively. The concentrations of Pb, Zn and Cd in their substrates were 16.86, 54.58 and 0.30 mg·kg^-1 respectively, being lower than the background values in Guizhou Province. Correlation analysis showed that the concentrations of Pb, Zn and Cd in bryophytes were not correlated significantly with those in their substrates (P>0.05). The results indicated that bryophytes not only had a strong ability to absorb and reserve water, but also had a high adsorptive ability of heavy metals from automobile exhausts. Therefore, they had an important significance for stabilizing road slopes in karst areas and environmental purification.