Objective To analyze the economic burden due to healthcare-associated infection (HAI) in low birth weight (LBW) infants, and provide theoretical basis for formulating HAI related policies. Methods The data of LBW infants in a tertiary first-class hospital from January 2018 to December 2022 were retrospectively collected. Propensity score matching method and marginal analysis were adopted to evaluate the economic losses in LBW infants and hospitals due to HAI. Results A total of 1 048 LBW infants were included in analysis, 124 of whom had HAI, with HAI incidence of 11.8%. A total of 109 pairs were successfully matched using the propensity score matching method. The median length of hospital stay for LBW infants in the HAI group and non-HAI group were 34.0 and 11.0 days, respectively, the length of hospital extended 23 days in LBW infants in the HAI group (P < 0.001). The median hospitalization expenses for LBW infants in HAI group and non-HAI group were 38 067.6 and 12 375.7 Yuan, respectively, the hospitalization expense for LBW infants in HAI group was 25 691.9 Yuan more than non-HAI group (P < 0.001). The major increased expenses were examination, treatment and medication fees. The total hospitalization expenses in different birth weight LBW infants in HAI group were all higher than non-HAI group, and the differences were all statistically significant (all P < 0.05). LBW infants with gestational age < 32 weeks had longer length of hospital stay and higher total hospitalization expense, differences were all statistically significant (all P < 0.05). When the marginal profit ratios were 5%, 10%, and 15%, respectively, the economic losses caused by HAI were 371 000 Yuan, 742 000 Yuan, and 1 114 000 Yuan, respectively; The ratios of loss-profit and loss-profit to infection coefficient were 0.33 and 2.79, respectively. Conclusion HAI cause significant economic losses to both LBW infants and hospitals. Infants with a birth weight ≤ 1 000 g and those with a gestational age < 32 weeks are key populations for prevention and control. The lost-profit to infection coefficient can be used to estimate the economic loss of the hospital, timely adjust infection control measures, and reduce the incidence of HAI.