With the formulation of different policies, special economic zones dramatically expanded in the past 40 years. Basing from remote sensing and geographic information system technology, we performed long-term and high-frequency monitoring of urban expansion in special economic zones by using multi-source remote sensing images between 1973 and 2013. Shenzhen, Xiamen, and Haikou were selected as research subjects. All spatial expansion information was obtained through human-computer interactional digital interpretation. Basing from established-interpretation symbols of urban lands, researchers with experience in visual interpretation referred to Google Earth and topographic maps to ensure the accuracy of monitoring results above 90%. This study selected expansion speed, influences on land use, compact ratio, and centroid shift as indicators, and combined the effects of natural and man-made elements to analyze the similarities and differences of spatiotemporal characteristics among Shenzhen, Xiamen, and Haikou. Four major results were obtained. First, the expansion speed of special economic zones in the past 40 years experienced one low-speed stable stage, two acceleration stages, and two deceleration stages. The expansion speed of Shenzhen was the fastest, followed by Xiamen and then Haikou. This situation fully reflects the significance of national and local policies, as well as social and economic development. Second, 1370.61 km2 nonurban lands around Shenzhen, Xiamen, and Haikou were converted to urban land between 1973 and 2013. Arable land was the first land source of special economic zone urban expansion. Other main land sources of urban expansion include forest land, water body, rural settlement, industrial and traffic lands, and sea area. Grassland and unused land had minimal contribution to urban expansion. Rural settlement and industrial-traffic land was the second land source of Xiamen and Haikou urban expansions, and the third land source of Shenzhen urban expansion. Forest land was the second land source of Shenzhen urban expansion but produced a contribution rate of <10% to Xiamen and Haikou. Third, the compact ratio of special economic zones decreased. Before 2004, land resources around special economic zones were relatively adequate, urban expansion was fast, land-use efficiency was low, and compact ratio considerably reduced. After 2004, urban expansion space was limited, expansion speed slowed down, and compact ratio stabilized. Fourth, marine reclamation engineering appeared during urban expansions in Shenzhen, Xiamen, and Haikou. Under the combined effects of the policies and marine reclamation engineering, the centroid of special economic zones tended to migrate toward the coastline. Affected by the comprehensive influence of expansion area and compact ratio, Shenzhen and Haikou had the large stand smallest centroid shift distances, respectively. Remote sensing monitoring of expansions in special economic zones can provide support for the future projection and policy formulation of special economic zones.