Alluvial fans serve as useful archives that record the history of depositional and erosional processes in mountainous region and thus can reveal the palaeoenvironmental change. The interpretation of these archives, however, is problematic because the accumulated sedimentary deposits of fan systems tend to be poorly exposed and few such systems have been the focus of investigation using highresolution subsurface analytical techniques. To overcome this limitation of standard outcropanalogue studies, a geophysical survey of a coastal alluvial fan was performed using groundpenetrating radar (GPR) to devise a scaled threedimensional subsurface model. The coastal alluvial fan in the northern Haitan island in Fujian province was selected as a case study and a network of about 700 m sections of GPR was surveyed. GPR penetration depth reaches about 20 m, and data interpretation was based on classification into nine distinct radar facies. Nine radar facies were grouped into unconformities and bed structure, which completely reflect that the megadune consists of two alluvial fans. Combining the geological investigation and grainsize analysis, we assumed that the development process of such coastal alluvial fan can be divided into four stages: ①During the last interglacial period of late Pleistocene, “Old Red Sand” formed “Red Desert” in the coastal zone; ②During the late glacial, weathering clastic materials, derived from the mountainous regions, poured and stacked on the coastal zone, and then formed alluvial fan covered above the erosion surface of “Old Red Sand”; ③During the earlymiddle period of Holocene, the river cut down the alluvial fan to form the basic shape of the great sandy hill; ④During the late Holocene, windsand activity shaped the geomorphic feature of the modern great sandy hill. The research is benefit for further understanding of the evolution of palaeoenvironmental change in the coastal zone of Fujian province. The results of the integrated outcropgeophysical approach encourage similar future studies on alluvial fans to retrieve their depositional history.