This paper explored the impact of prenatal maternal stress on antenatal depressive symptoms andthe mediating effect of subjective well-being. By using the convenience sampling method，this paper adoptedpregnant women in the obstetrics outpatient department of a general tertiary hospital in Nantong as samples andinvestigated their general demographic characteristics through questionnaires. The paper utilized the PregnancyStress Rating Scale(PSRS)，Edinburgh Postpartum Depression Scale(EPDS)and Subjective Well-being Scalefor Chinese Citizens(SWBS-CC20)to measure their psychological state. This paper used the statistical softwareSPSS 27.0 for descriptive analysis and adopted SPSS macro program PROCESS for mediation effect analysis.The results showed that among 653 pregnant women，the incidence of depressive symptoms was 34.0%，and theincidence of moderate to severe prenatal depressive symptoms was 9.2%. The relationship between pregnancystress，subjective well - being，and prenatal depressive symptom showed that the higher the stress duringpregnancy，the higher risk of prenatal depressive symptoms(β=0.262，P＜0.001)with lower subjective well-being(β=-0.284，P＜0.001). The higher the subjective well-being，the lower the risk of having antenatal depressivesymptoms(β =-0.246，P＜0.001). Subjective well-being partially mediated the relationship between prenatalmaternal stress and antenatal depressive symptom，with the mediating effect accounting for 26.21% of the totaleffect. Prenatal maternal stress significantly and positively predicted antenatal depressive symptoms. This studysuggests that we should focus on reducing prenatal maternal stress and continuously improving subjective well-being to alleviate the occurrence of antenatal depressive symptom.