Abstract: Objective To explore the best time period of pulse oximetry in congenital heart disease (CHD) screening. Methods Totally 5433 newborns delivered or treated in Ningbo Women and Children’s hospital were enrolled in the study. Cardiac color ultrasound was used to arrive diagnosis and every screening time period (0 ~ 24 h、24 h ~ 48 h、48 h ~ 72 h) was analysed. Results Among the three time periods: the sensibility was in the range of 54.72% ~ 67.92%, specificity was 99.11% ~ 99.61%, false negative rate was 32.08% ~ 43.40%, false positive rate was 0.39% ~ 0.89%, Youden index was 0.54 ~ 0.68, coincidence rate was 98.67 ~ 99.30, and kappa was 0.44 ~ 0.65. Conclusion The best screening time is the period between 48h and 72 h after birth.