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Lucerne root growth not only affects the ability of lucerne cultivars to assist soil conservation, but is the primary pathway for the plants to absorb water and nutrients. Therefore, the study of root development is important for assessing the suitability of lucerne cultivars to semi-arid environments. A field experiment was conducted during 2000-01 in the semi-arid and and region of west China to study the suitability of one local and seven introduced lucerne (Medicago sativa) cultivars by comparing their root development. The total number of secondary roots and taproot length were significantly different between lucerne cultivars after only one dry season. Sixty-five percent of secondary roots were present during vegetative growth, and 40% of secondary roots arose within the 10-20 cm depth. Root biomass and fine root volume were also significantly different between the eight cultivars, and the increase in the rate of development of fine root volume and root biomass in the cultivars ’sandili’ and ’Amerigraze401+Z’ was significantly faster than those of the other six cultivars, indicating that ’sandili’ and ’Amerigraze401+Z’ were better adapted to semi-arid conditions. Fine root volume and root biomass of all cultivars decreased with depth, except for those of ’sandili’ and ’Amerigraze401+Z’ where fine root volume and root biomass at 20-30 cm depth was greater than that at 10-20 cm. Using secondary roots, taproot length, fine root volume, and root biomass as analysis factors, cluster analysis results suggested that ’sandili’ and ’Amerigraze401+Z’ are suitable for sowing in the semi-arid and and conditions of west China due to their strong root development.