A prerequisite for the protection and governance of mountainous areas is the scientific evaluation of the population carrying capacity, which depends on an accurate assessment of population density. The prior method of calculating population density does not consider the effect of the relief degree of land surface (RDLS) on population distribution. Therefore, it cannot accurately reflect the degree of population aggregation, especially in mountainous areas. Thus, this study selects the Upper Minjiang River Basin as the research area and introduces the RDLS and elevation factor. First, it extracts the exact population value by means of geographic information system technology. Second, it conducts the correlation analysis between the population distribution and the RDLS by using the Statistical Package for Social Science (SPSS). Then, based on the correlation and the population distribution analysis, this method is used to determine the appropriate standard of RDLS and elevation in different mountainous areas. According to the corresponding results, it calculates and corrects the population density of the upper Minjiang River Basin. The results show that: 1) The population distribution of the upper Minjiang River Basin is strong affected by RDLS, correspondingly, the R2 value between the RDLS and the population of the upper Minjiang River Basin is 0.89. The correlation coefficients between the RDLS and the population density of different county (Wenchuan county, Mao county, Li county, Heishui county and Songpancounty) are 0.841, 0.773, 0.643, 0.696 and 0.730, respectively. 2) The RDLS and elevation are introduced to revise the population density in the upper Minjiang River Basin. According to the results of the population cumulative distribution curve, the rational RDLS for human habitation in Wenchuan County, Mao County, Li County, Heishui County and Songpan County are 3.2°, 4°, 4.3°, 4.4° and 4.2°, respectively. The corresponding elevation is 3 693 m, 4 033 m, 3 790 m, 3 853 m and 3 966 m. 3) The population density has been corrected is clearly different from the previous result. The higher RDLS of mountainous areas, the more obvious discrepancy exists. For example, compared with previous result, the revised population density in Li County and Heishui County increase by 7.8 and 5.6 times, respectively. In contrast, the revised population density in Wenchuan county and Mao county increase by 2.3 and 2.4 times, respectively. 4) The upper Minjiang River Basin is confronted with greater pressure of population growth. Thus the population distribution of this area should be guided by local social, economic, topographic and other conditions. Specifically, Wenchuan county and Mao county should adopt intensive development strategy, Li County and Heishui County should adopt moderate development strategy and Songpan County should adopt ecology repair strategy.