Recent decades have witnessed a drastic shift in the spatial structure of China's large cities, from being monocentric to polycentric; however, the existing literature has not completely identified the transformation process, due to a lack of investigation from employment distribution. By using enterprise registration data from 1996, 2001, and 2010, this paper aims to fill the research gap by examining employment subcenters and their effect on population distribution in Beijing. We found that (1) the number of employment subcenters increased from 6 in 1996 to 11 in 2001, and to 16 in 2010; and (2) the population distribution in 2000 was not significantly affected by the appearance of employment subcenters, while the population distribution in 2010 was significantly and positively impacted by distance to the nearest subcenter. These results justify the trend of Beijing becoming a polycentric city. [ABSTRACT FROM AUTHOR]