Objectives. To describe the incidence, risk factors, and potential causes of preterm birth (PTB) in China between 2015 and 2016.Methods. The China Labor and Delivery Survey was a population-based multicenter study conducted from 2015 to 2016. We assigned each birth a weight based on the sampling frame. We calculated the incidence of PTB and the multivariable logistic regression, and we used 2-step cluster analysis to examine the relationships between PTB and maternal, fetal, and placental conditions.Results. The weighted nationwide incidence of PTB was 7.3% of all births and 6.7% of live births at 24 or more weeks of gestation. Of the PTBs, 70.5% were born after 34 weeks and 42.7% were iatrogenic. Nearly two thirds of all preterm births were attributable to maternal, fetal, or placental conditions, and one third had unknown etiology.Conclusions. This study provided information on the incidence of PTB in China and identified several factors associated with PTB. The high frequency of iatrogenic PTB calls for a careful assessment and prudent management of such pregnancies, as PTB has short- and long-term health consequences.