Desert ecosystem is an important subsystem of the terrestrial ecosystem, but the desert ecosystem is very fragile. Scientific research on the spatio-temporal pattern of ecosystem service value in desert regions is of great significance for the implementation of desert ecological environmental protection policies, ecological security construction and sustainable development of desert regions. This paper selected Ulan Buh Desert as the research area, collected four phases land use data of 1990-2018. Based on the equivalent factor method, the spatio-temporal dynamic characteristics of ecosystem service value in Ulan Buh desert in the past 30 years were explored by using grid analysis, hot spot analysis, trade-offs and synergies analysis, the driving factors for its formation were also discussed. The results showed that: (1) the total value of ecosystem services first decreased and then increased gradually from 17.03 billion yuan in 1990 to 25.94 billion yuan in 2018. The contribution of regulating services value was the largest among all ecosystem services, accounting for 71.34% on average, and the provisioning services increased by 85.04% in the past 30 years, which was the biggest among all ecosystem services. But the ecosystem service value was still dominated by water, desert and cultivated land, and the regional ecological security was unstable to some extent. (2) The spatial distribution of ecosystem service value was characterized by high value in the east and northeast and low value in the southwest and middle part. This was mainly related to the land use distribution in this area: to the east is the Yellow River, to the northeast is the Hetao Plain, and in the middle and southwest are deserts and saline-alkali lands. The spatial pattern was basically unchanged from 1990 to 2010, while the high-value area was expanded in 2018. (3) From 1990 to 2018, the proportion of the cold spot area increased from 2.85% to 4.23%, and the proportion of the hot spot area increased from 0.22% to 10.45%. Hot spots were distributed along the Yellow River and part of the ecological recovery areas in the northeast, but the cold spot area near the Jilantai Salt Lake increased gradually, which should be taken seriously in ecological management. (4) From 1990 to 2018, the relationship between ecosystem services was primarily synergies, and the trade-offs existed between provisioning services and other ecosystem services in 1999-2000. From 2000 to 2018, ecosystem services were all in synergies, and the degree of synergy increased with time.