The relationship between the population (or effective labor) scale and technical progress will help to explain the transition of different stages of economic development:in the "Malthusian Trap" stage, the technology of agricultural production increased slowly, the population also increased gradually, the market expanded gradually, so the industrial enterprises can afford greater fixed(innovation) cost, production innovation started, human get rid of the " Malthusian trap"; After a certain stage of economic development, it would also face demographic transition, and fall into the "middle income trap", this time could no longer rely on population growth simply, but on the accumulation of human capital to increase the scale of effective labor, and further promote the innovation of industrial enterprises, thus to lay the foundation for getting rid of the "middle income trap". The expansion of the scale of effective labor would not only promote technological progress through positive spillovers, but also speed up technological progress directly by reducing the cost of innovation of industrial enterprises. Based on the establishment of the two period overlapping generations model including four departments (agricultural production (service) department, industry department, household sector and government), the results of numerical simulation analysis showed that adequately prolonging the period of labor, reducing the contribution rate of the old-age security account in the aged and the degree of bequest were beneficial to encourage the residents to increase their labor supply, accumulate human capital, and then promote technological progress, and finally get rid of the growth trap.