The changes in China’s family planning policy in recent years have led to changes in the age structure of pregnant women, and the prevalence of postpartum depression (PPD) is also on the rise. Cognitive Behaviour Training (CBT) as an effective intervention is widely used for postpartum depression. However, the shortage and health disparities of mental health resources, the stigma of postpartum depression in postpartum women and the need for postpartum recovery and child care prevent postpartum women from seeking traditional face-to-face CBT. Therefore, the purpose of this proposed study is to examine the effect of mobile phone applications (App) based CBT on postpartum depression, anxiety, pressure and parenting sense of competence. A double blind, randomized controlled trial will be used in this study to examine the effectiveness of App-based CBT in reducing the prevalence of postpartum depression compared with usual postpartum care in China. A total of 120 participants will be recruited in this study. The intervention consists of a weekly theme module app for continuous six weeks, each module including learning content and assignments. The control group received usual postpartum care content through the App. Outcome measures include postpartum depression, anxiety, pressure and parenting sense of competence at 0-, 3- and 6-month after the intervention. If our intervention is effective, it will provide a time-friendly and unrestricted intervention for the psychological care of perinatal women, which can effectively solve the shortage and unevenness of mental health resources. Chinese Clinical Trial Registry, ChiCTR1900020735 . Registered 15 January 2019.