Objective To study the impact of sucrose analgesia on pain response and salivary cortisol levels in preterm infants.Method Preterm infants admitted to our hospital between January 2014 and October 2016 with gestational age ＜ 34 weeks,birth weight ＜ 2 000 grams,and length of hospital stay ≥ 14 days were prospectively assigned into two groups.The intervention group received 0.3 ～ 0.5 ml of 12％ sucrose solution two minutes before each painful procedure,while the control group received none.At time of discharge and at 8 months of corrected age (CA),pain response was measured,saliva samples were collected and salivary cortisol levels were assayed using Enzyme Immunoassay Kit before and after pain stimulus.Result A total of 82 infants were included in our study,42 in the intervention group,and 40 in the control group.There were no statistically significant differences between two groups in pain response at discharge and 8 months of CA.At time of discharge and at 8 months of CA,infants in intervention group had higher salivary cortisol levels than in control group at time of discharge and 8 months of CA after pain stimulus [6.8 (5.6,11.7) ng/ml vs.5.4 (2.6,10.8) ng/ml,5.0 (3.3,5.6) ng/ml vs.4.8 (3.0,5.5) ng/ml] after log transformation,two groups were statistically significant (P ＜ 0.05).However,before the pain stimulus,no differences were found between two groups.Multiple stepwise regressions analysis showed that salivary cortisol level post pain stimulus was negatively related to the total number of pain stimulus,and positively related to sucrose analgesia at discharge and 8 months of CA.Conclusion Sucrose analgesia may mitigate the negative effect of repeated pain stimulus on cortisol regulation in preterm infants,however,may have no influence on pain response of them.