Facial expression processing has long been regarded as the most important part of interpersonal communication. The communication between mother and baby largely depends on whether the mother can correctly interpret the facial expressions of the baby, which is crucial to establish a good mother-infant relationship and the healthy development of the baby's body and mind. The study found that mothers read their babies' facial expressions better than other groups of people, and that this effect was present in the early days of the baby's birth, leading some to speculate that pregnancy alters a woman's processing of facial expressions. Less is known about facial expression processing in pregnant women compared with postpartum mothers. In recent years, researchers have studied the facial expression processing characteristics of pregnant women from behavioral and neurophysiological aspects, mainly through perceptual processing and attentional bias. This paper sorted out the research methods, theoretical basis and research status of the cognitive processing characteristics of pregnant women's facial expression, in order to understand the impact of pregnancy on women's facial expression processing, hoping to provide reference and new research ideas for future research.