Objective To analyse the risk factors associated with spontaneous intestinal perforation (SIP) in extremely premature infants/extremely low birth weight infants. Method From January 2015 to December 2018, infants with gestational age (GA)<28 weeks or birth weight (BW)<1000 g admitted to our neonatal intensive care unit were enrolled to the retrospective nested case-control study.The clinical data of SIP infants (SIP group) and infants with the same GA but without SIP (control group) were randomly selected and compared. Multivariable Logistic regression was used to analyse the risk factors of SIP. Result A total of 409 extremely premature infants/extremely low birth weight infants were born during the study period. Among them, 25 SIP infants and 55 controls were enrolled. The incidence of SIP in infants with GA 22～25 weeks was 11.8％(16/136), which is higher than infants with GA 26～27 weeks (2.0％, 5/247) (χ2=16.057, P<0.001). The incidence of SIP in infants with BW 400～749 g was 13.0％(14/108), which is higher than infants with BW 750～999 g (3.4％, 8/236) (χ2=11.343, P=0.001). Multivariate Logistic regression analysis showed that twins (OR=4.153, 95％CI 1.392～12.384, P=0.011), umbilical veins catheterization (OR=15.942, 95％CI 1.026～247.789, P=0.048) and ibuprofen use within 3 days after birth (OR=15.387, 95％CI 1.519～155.883, P=0.021) were independent risk factors of SIP. Conclusion The smaller the GA and BW, the higher the incidence of SIP. Twins,umbilical veins catheterization and ibuprofen use early after birth may be independent risk factors of SIP.