Nature-based recreation has become an important activity in contemporary society and a key component of cultural ecosystem services. Although the methods of mapping the outdoor recreation supply have been gradually improved, few studies have carried out multi-temporal evaluations. Based on land use/land cover (LULC), POI, and other web-open data, we mapped the recreational service supply in Shanghai in 2008 and 2018, combining recreation potential and recreation opportunities. We first selected the evaluation indicators, using LULC to measure recreational potential, and POI density and accessibility to measure recreational opportunities. Then, we used principal component analysis (PCA) to determine the weights of the 12 factors that measure recreational opportunities, and made RO and RP maps, respectively. Finally, we overlaid RO and RP maps to obtain the spatial distribution map of recreation service supply. Our results showed that the supply of recreation services in 2008 and 2018 presented a “V-shaped” gradient along the city center areas—the peri-urban areas—the rural areas. Compared with the year 2008, the average recreation value decreased in nine regions, but increased in Chongming District in 2018. The assessment and mapping of recreation service supply value provide a basis for the development of local recreational resources, land use decisions, and the management of recreational cultural ecosystem services.