In the context of the deepening of aging in China and the decline of birth rate, this paper attempts to construct a theoretical model from the CES production function, and derives the influence mechanism of population structure and technological progress bias on China"s labor income share. And based on China"s 1990-2017 panel data research, China"s elements are complementary, and technological progress is biased towards capital. It is confirmed that the change of population structure in China--the rise of the old-age dependency ratio and the decline in the dependency ratio of children have a negative impact on the share of labor income in China. At the same time, the capital-biased characteristics of China"s technological progress have reduced the share of labor income in China. After controlling for other factors, sub-regions, and rejection of outliers, the results are still significant.