Objective: To understand the parental stress of fathers of preterm infants, and analyze the influence of positive psychological capital and social support on parental pressure, so as to provide reference for the psychological care of fathers of preterm infants. Methods: From July 2018 to July 2019, 238 preterm fathers were selected, parents’ stress scale, positive psychological capital questionnaire and social support scale were used. Results: The scores of parental stress, positive psychological capital, and social support were 89.39±16.45, 112.34±10.37, and 42.11±10.98, respectively. There were significant differences in parental stress scores among fathers with different hospitalization time, neonatal complications, primipara or not, and family per capita monthly income (P<0.05). The scores of all dimensions of parental stress was negatively correlated with the scores of all dimensions of positive psychological capital and social support (r=−0.532 to −0.170), and the data was statistically significant (P<0.05). Optimism, hope, resilience, self-efficacy and social support were all independent factors (P<0.05), 48.0% of variance could be explained (corrected R2=0.480). Conclusion: The level of parental stress in preterm fathers is relatively high. Positive psychological capital and social support are independent influencing factors of parental pressure.