Depression and parenting stress are common phenomenon in postpartum women. Both of them increase risks for the development of psychopathology in the children. Risks of maternal depression on children might be transmitted through four mechanisms, such as heritability of depression, innate dysfunctional neuroregulatory mechanisms, parenting and stressors. Maternal depression is related to children’s behavior problem, such as negative affect, heightened emotionality, anxiety. Parenting stress can be seen as resulting from a perceived discrepancy between demands pertaining to parenthood and personal resources. Such stress can be experienced in several areas of life connected to parenting. More parenting stress could predict children’s anxiety, depression and so on. Therefore, this study aimed at exploring the possible relationship between maternal depression and maternal parenting stress by using a cross-lagged design, and construct a moderated mediation model in which parenting stress mediated the relationship between maternal depression and toddlers’ internalizing problem behavior, and this mediation effect was moderated by mother’s education. 　　A sample of 298 mothers and their six month infants was recruited in the longitudinal study for 8 months. Mothers were asked to complete Edinburgh Postnatal Depression Scale, Parenting Stress Index in Time 1 and Time 2, and complete the Infant-Toddler Social and Emotional Aseessment in Time 2. The results indicated that: (1) Time 1 maternal depression could predict Time 2 maternal parenting stress after controlling mother’s education and Time 1 maternal parenting stress (β=.136，p<.05) . However, Time 1 maternal parenting stress could not predict Time 2 maternal depression after controlling mather’s education and Time 1 maternal depression (β=-.098，p>.05) . (2) Maternal parenting stress played partial mediating effect between maternal depression and toddlers’ internalizing problem behavior. That is, maternal depression not only had a direct influence on toddlers’ internalizing problem behavior, but also aggravated toddlers’ internalizing problem behavior through mothers’ parenting stress. This mediation effect was moderated by mother’s education. For low education mothers, parenting stress significantly predicted toddlers’ internalizing problem behavior (β=.376，p<.001); For high education mothers, parenting stress couldn’t predict toddlers’ internalizing problem behavior significantly (β=.052，p>.05). 　　All in all, these findings highlighted the mediation effect of maternal parenting stress and moderated effect of mother’s education in the relationship between maternal depression and toddlers’ internalizing problem behavior. Mothers’ high education could significantly reduce the negative effect of maternal parenting stress on toddlers’ internalizing problem behavior. It is important to pay more attention to depressed mothers, and give them much help on their daily life and parenting practices. All these help will be beneficial to children’s mental development. In one word, these results has important theoretical and reference value to maternal parenting.