【Objective】To  investigate  the  association  between  fetal  fraction （FF） of  cell- free  DNA  and  adverse pregnancy outcomes. 【Methods】A retrospective case- control study was conducted in 1 231 Chinese pregnant women who underwent non-invasive prenatal testing and gave birth to their children in the Third Affiliated Hospital of Sun Yat- sen University during January 2017 to October 2018，including HDP group（n = 84），FGR group（n = 57）and preterm birth group（n = 59）as case groups，and the pregnant women without pregnancy-related complications were included in the control group（n = 1 031）. The correlation between FF and maternal age，gestational weeks，body mass index（BMI）， and comparison of FF difference in different groups were analyzed.【Results】In 1 031 normal pregnant women performed NIPT，the plasma FF was（12.03 ± 3.64）% ，FF and maternal BMI were negatively correlated（rs = -0.079，P < 0.05）. FF in HDP，FGR，preterm birth group were（11.21 ± 2.60）%，（12.48 ± 3.92）%，（11.66 ± 3.34）% ，respectively. Compared with control group ，FF in HDP group was statistically lower ，OR = 0.926，95%CI：0.859-0.997，P = 0.043. FF in FGR group and preterm birth group were not statistically different compared with control group.【Conclusions】Low FF is a risk factor of HDP

and we may apply FF of cell-free DNA to predict the risk of HDP in further research. The correlation of FF and FGR

preterm birth have not been found yet.