The forest resources of Chongming serve as a crucial natural foundation for the ecological development of Shanghai. This study focused on the forests of Chongming Island as the research subject and established an accounting indicator system for the Gross Ecosystem Product (GEP) of these forests. Based on this framework, the GEP of the forests on Chongming Island in 2022 was calculated and analyzed. The results indicated that the GEP of Chongming Island’s forests is approximately 940 million RMB annually, with an average per-unit area value of about 30 000 RMB per hectare. The composition of value is predominantly regulatory services (473 million RMB/year) and material products (402 million RMB/year), whereas cultural services (64.57 million RMB/ year) contribute comparatively less, representing 50%, 43%, and 7% of the total GEP, respectively. Among material products, forest fruits are the principal component, with an estimated value of 273 million RMB/year, accounting for 67.88% of the total value of material products. Regulatory services mainly comprise oxygen provision, local climate regulation, water conservation, and fl ood control, with a total value of approximately 405 million RMB/year, accounting for 85.66% of the total value of regulatory services. In terms of spatial distribution, the highest total values for the four categories of regulatory services were observed in Dongping Town and Miao Town. However, the peak value per unit area was recorded in the Dongping Forest Farm. Cultural services are primarily driven by recreational activities, with a value of approximately 42.17 million RMB/year, accounting for 65.31% of the total value of cultural services. The GEP accounting framework for Chongming Island’s forests developed in this study provides a foundational methodology for forest GEP assessments across Chongming and, by extension, Shanghai. Furthermore, it provides a scientifi c basis for establishing horizontal eco-compensation mechanisms and refi ning value-realization pathways for ecosystem products in Shanghai’s forestry sector.