Introduction The demographic profile of China has often been seen as that of the most populous country in the world, with traditionally high fertility, rapidly growing, mainly rural population, and a young age structure. But suddenly it is found that such a description is no longer true. Fertility has dropped to below replacement level, and the population is rapidly aging, sex unbalance among the new-born has been an issue for more than two decades, and the volume of internal migration has become the largest in world history during peace time. China will soon lose its position as the world’s most populous country to India. Demographic transformation in China has been so swift that it is necessary to update our understanding of population dynamics in China, particularly with the arrival of low fertility. This chapter will first provide a review of fertility trends and fertility policy in China followed by an explanation of low fertility based on the evidence from an on-going survey in Jiangsu province. The impact of low fertility with respect to population aging, gender equality, sex ratio at birth and labor supply will then be presented, and the chapter will end with a discussion suggesting that more work needs to be done to understand the population dynamics along with the arrival of low fertility in China.