The spatial distribution patterns of plant populations are the results of the combined effects of various ecological processes. Exploration of the spatial patterns and their driving mechanisms of plant populations is helpful in elucidating the ecological adaptation strategy of a population and maintenance mechanism of the community. To understand the spatial patterns and their formation mechanisms of the dominant species in desert steppes in Ningxia, four 10 m×10 m sample plots which dominated by Agropyron mongolicum, Stipa breviflora, Lespedeza potaninii, Cynanchum komarovii were established, respectively. The spatial coordinates of the dominant species were measured by using adjacent lattice method. Their spatial distribution patterns were analyzed based on complete spatial randomness null models, and their driving factors were explored based on heterogeneous poisson process null mode and poisson cluster process null model. The results showed that (1) when using complete spatial randomness null model, all populations presented the aggregated distribution at < 4 m scales and random and uniform distributions at larger scales. (2) By using heterogeneous poisson process null model, the four dominant species mainly showed random distributions, but the S. breviflora, L. potaninii and C. komarovii departed from heterogeneous poisson process at much smaller scales. (3) The measured values of four species were accordance with poisson cluster process null model at the 0-5 m scale, appearing as random distribution. In conclusion, the four dominant populations mainly appeared as aggregated distribution. The spatial patterns of the dominant species were driven together by habitat heterogeneity and dispersal limitation in desert steppe in Ningxia. Relatively, the dispersal limitation played more significant roles at the small spatial scale.