If and how to regulate the population scale has been an important issue for the most megacities'government in China in the background of popular "urban disease". This paper studies the regulating measures of population scale of megacities from the perspective of population carrying capacity,and puts forward that the employment-oriented economic factor is the direct and crucial factor influencing the regional population carrying capacity,and other factors are indirect factors as cost factors of economic factor. Moreover,the conclusion is described mathematically on the basis of the production function theory of economics,and the related simulation analysis is also carried out based on Beijing's data. On these basis,there is a conclusion that regulating population scale by administrative measures is unreasonable,and population controlling of megacities should be realized by industrial controlling and reconstructing and scientific city planning.
