The use of the difference between ecological footprint and biocapacity to evaluate the sustainable development of a country may be biased. Therefore, we discuss the nonlinear impact of the ecological footprint on biocapacity from the perspective of the self‐regulation capacity of the ecosystem, which provides a new perspective for evaluating the sustainability of a country. Using panel data of the G20 countries, this study establishes a panel smooth transition model with a continuous transition process, which abandons the constraints of linear models and agrees with the gradual characteristics of ecosystem evolution. The results show that: (1) For the G20 countries, the influence of ecological footprint on biocapacity presents an inverted “U” curve. (2) From the perspective of the degree of development of a country, the growth of the ecological footprint of a developing country will weaken its biocapacity, whereas that of a developed country will enhance its biocapacity. (3) Economic growth weakens biocapacity, and overheated economic growth may have an irreversible impact on the ecosystem. (4) Technological progress and population density growth will enhance biocapacity.