The Third Plenary Session of the 20th Central Committee of the Communist Party of China decided to "establish a tired and categorized assistance system for low-income rural populations and underdeveloped regions". Scientific identification of underdeveloped regions is the foundation for establishing a tired and categorized assistance system and narrowing regional development gaps. This paper constructs a conceptual framework of endogenous development impetus for underdeveloped regions from nine indicators across three dimensions: economic growth, social development, and ecological environment. Using the AF method, it conducts an analysis of the endogenous development impetus shortcoming index for the identification of underdeveloped regions based on 1,433 valid county-level samples in 2022. The research finds that when considering the simultaneous existence of five or more indicators with shortcoming, a total of 452 underdeveloped counties and 175 acute underdeveloped counties were identified among the sample counties. The contribution rates of the three dimensions of economic growth, social development, and ecological environment to the shortcoming index of underdeveloped regions are 0.471, 0.399, and 0.130, respectively. According to the decomposition of indicators, the contribution rates of county-level economic aggregate, fiscal level, and education level are the top three in sequence, and the contribution rates of the three indicators in the ecological environment dimension are ranked as green coverage, sewage treatment, and garbage treatment. The degree of underdevelopment of special type regions from high to low is as follows: national key counties for rural revitalization assistance, poverty-stricken counties, ethnic minority counties, ecological function zone counties, revolutionary old area counties, and land border counties. Underdeveloped regions are mainly distributed in the western and central regions, and there are also underdeveloped regions in the eastern region. This paper proposes to tired underdeveloped regions based on the number of indicator shortcomings and categorize them according to the contribution rates of each indicator to the shortcoming index. It also suggests constructing a central fiscal transfer payment factor for special type regions based on the degree of shortcoming to formulate more targeted transfer payment policies. This paper provides a scientific basis for establishing a tired and categorized assistance system for underdeveloped regions during the "15th Five-Year Plan" period.