To explore the DNA polymorphism of Glb 1 genes in maize landraces from Southwest China, we cloned and sequenced the DNA sequences from 40 maize landraces, and downloaded the homologous sequences of 19 individuals representing common maize, parviglumis, Z. luxurians, and T. dactyloides from GenBank. By aligning these sequences and analyzing DNA variations in Glb 1 loci, we found 35, 25, 33 and 25 polymorphism sites in maize landraces from Sichuan, Chongqing, Yunnan, and Guizhou, respectively. Their genetic polymorphisms were 87%, 86%, 85%, and 71% of that in parviglumis. On the basis of estimates of per base pair and per base pair, the highest level of sequence variation was found in parviglumis, followed in turn by maize landraces from Sichuan, landraces from Chongqing, landraces from Yunnan, landraces from Guizhou, common maize, T. dactyloides, and Z. luxurians. The estimates of Tajima's and Fu and Li’s D statistic for Glb 1 gene were negative in the eight taxa, suggesting that neutrality cannot be rejected. In comparison, more fixed differences than shared polymorphisms between maize landraces and parviglumis, Z. luxurians, as well as T. dactyloides were found. The genealogical and network analysis provided the evidence for the genus Zea taxonomy. Additionally, genetic diversity of landraces was greater in Sichuan than in the other three regions. This result supports the hypothesis that the first maize migration was from India to Sichuan by way of Tibet in China.