Abstract: Dual evaluation, as the basic work of territorial space planning, has attracted much attention. Based on the perspective of territorial space planning, this paper explored the theory and method of dual evaluation, reorganized and scientifically defined the concepts of key terms such as resources, environment, carrying capacity, dual evaluation, "Industrial-living-ecological" space and "urban construction-agricultural production-ecological protection" space. In the practice of the dual evaluation in Fujian Province, the simple model method and NPP method were used to evaluate the importance of ecological protection and identify the ecological protection space. According to Cannikin Law, using the weighted summation method and the limiting factor method, the suitability of land space development for different functions including agricultural production and urban construction was evaluated, and the quantity and quality of agricultural production and urban construction space were identified. This paper provides data support for the pattern optimization of ecological security, agricultural development and urban construction, as well as the delineation of "three areas and three lines" in Fujian Province.