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Integrated regional studies are important tools for understanding dune geomorphology. As a part of an integrated regional study of dune geomorphology in the Kumtagh Sand Sea, northwestern China, we described the dune types and their distribution. In this paper, we propose a tentative dune classification scheme for these dunes based on previous schemes. We identified 11 main types of dunes, described their distribution, and estimated the areas they covered. Dunes generally became more complex moving from the north to the south of the study area, and from the edges to the inner areas of the sand sea. The wind regime also became more complex moving towards the south due to the physical blocking and thermodynamic effects of the mountains and the Qinghai-Tibetan Plateau, as well as the increasingly complex underlying topography. The combination of these factors appears to be responsible for the observed spatial variation of the dune types. Dune heights were estimated from 1:100,000 topographic maps and remote-sensing images. More than 80% of the dunes in the Kumtagh Sand Sea were less than 100 m tall, but with a maximum height exceeding 300 m. Dune height increased from north to south, with the tallest dunes occurring near the southern mountains. This general distribution of dune heights suggests that dune height was determined by a combination of sediment availability, airflow patterns, the blocking effect of mountains, and the underlying topography.