Population studies are inseparable from the collection and application of basic population data. During the reform and opening up, Chinese government, all sectors of society, and even individuals have successively carried out the collection and analysis of many basic population data. The characteristics of various basic demographic data are different, but according to the standards of the quality of research, scale, openness, social recognition, and accuracy of the data, the basic data meeting the requirements of population studies should mainly include the following categories of data: census data, population regular registration data, population sampling survey data, and demographic and social survey data organized by academia. The collection and application of these data are of great significance to China’s population studies. This chapter will focus on the characteristics, problems, and application of these data.