Desert riparian forests, widely distributed in the basins of inland rivers of the northwest arid regions of China, are dominated mainly by Populus euphratica Oliv. and Populus pruinosa Schrenk species. The largest and most typical desert riparian forest is found along the Tarim River Basin and occupies over 350000 km². This forest plays an active role in climatic regulation, desert expansion control, river banks protection, channels stabilization and oasis conservation. The riparian forest not only protects the fragile desert ecological system but also acts as an irreplaceable natural barrier. The Tarim River riparian forest is highly prized in the Tarim Basin for its great ecological, economical and social benefits. As a consequence of the increase in human population, an excessive exploitation of soil and water resources in upper and middle reaches of the Tarim River, induced recession, nonbearing trees and death of a large area of the desert riparian forest beginning with the 1960s. These effects directly endangered projects for development of sustainable oasis agriculture and for maintenance of an ecological balance. The objective of this study was to elucidate the characteristics of gaps in the riparian forest, the disturbance regimes and causal factors of gaps and predict a developmental trend as a theoretical base to manage and realistically protect the desert riparian forest. The P.euphratica forests of the Nature Reserve Region of Luntai County in the middle reaches of Tarim River, is the only remaining original desert forest and the center zone of distribution for P.euphratica. The research plots were located in Luntai (84°15'E, 41°09'N). The expanded gaps and canopy gaps were investigated in a 0.64hm² plot in 2009, by identifying all gap makers and gap border trees and measuring their stems. The results show that gaps in the desert riparian forest were nearly elliptical in horizontal shape, and the average ratio of long axis to short axis for each gap was about 1.52 for expanded gaps (EG) and 2.31 for canopy gaps (CG).Gap density was approx 62.5 per hectare, and the area occupied by EG and CG in desert riparian forest landscape was 69.52% and 29.03%, respectively. The results also show that the natural disturbance frequency was 1.45%/a for EG and 0.61%/a for CG, and the return interval of canopy gaps was about 164 years. For most EG and CG, whose size were in the range of 40-200m², and 0-80m², respectively. The gaps were formed within the last 50 years, most of them being 20 to 30 years old, and their formation rate was about 1.30 gap hm^-2a^-1. Most gaps were created by a combination of stem breakage and natural death (95.73% of total gaps). The majority of gaps consisted of 2 to 5 gap makers with the 4 gap makers category being the most abundant group and the average number of gap makers was 4.1 per gap. The diameter at breast height (DBH) of most gap makers ranged from 5 to 25cm, and their height varied from 4 to 8m. The average area of EG and CG formed by each gap maker was 27.12m² and 11.32m², respectively. The structure of DBH classes of the gap border trees (GBT) show a normal distribution, but tree height classes show a left-skewed distribution. The average numbers of GBTs was 8.375 per gap. The average DBH of GBT was 73.1% higher than that of gap makers, indicating the gap disturbance was a frequent occurrence in the desert riparian forest, and the continuously declining level of underground water was the driving force of gap formation.