Objective To investigate the value of cervical length and fetal fibrin detection in predicting the preterm birth.Methods The pregnancy women with high risk factors for preterm birth,low risk factors for preterm and threatened preterm birth were chosen to measure the cervical length by sonography and fetal fibrin test.Results The pregnancy women with cervical length(CL)30 mm in the three groups had a preterm rate of 67.8%、58.8%、31.3% and were significantly higher than that of the women with CL30 mm.The pregnancy women with fetal fibrin detection were positive in the three groups had a preterm rate of 72.0%、63.5%、34.7% and were significantly higher than that of the women with fFN were negative.The specificity of CL combined with fFN were 86%、89.6%、87.8% in the three groups.Conclusion The cervical length by ultrasound and fFN detection are valuable in predicting preterm birth among the pregnancy women with low risk factors.Combined screening can improve accuracy of predicting premature delivery.