The neural basis of emotional processing is an important basic issue in emotional psychology, especially in affective neuroscience research. Numerous studies have indicated that the amygdala is involved in different stages of emotion recognition, processing, and regulation, and is a key brain area for emotional processing. This paper reviews the academic history of the emotional processing function of the amygdala, and summarizes it into three stages. In the third stage (i.e., from the beginning of research using positive and negative emotional stimuli until now), psychology and neuroscience continue to deepen our understanding of the function of the amygdala, and have discovered a cutting-edge topic—the emotional valence specificity of the amygdala. In this article, we show that there is a specific trend of the left amygdala on positive emotional stimuli, the right amygdala on negative emotional stimuli, and negative preference of bilateral amygdala. In other words, when both positive and negative emotional stimuli are presented, the bilateral amygdala shows significantly greater activation when processing negative emotions. We also explain the phenomenon of differences in activation of the amygdala based on emotional valence from the perspective of evolution, amygdala anatomy, and psychological processing. However, we must also be aware that the specificity of the amygdala to different valences is regulated by factors such as age, gender, socioeconomic status, attentional resources, and the prominence of emotional materials. More importantly, though the amygdala displays lateralization of activation caused by different emotional valences, the functional connectivity between the amygdala and other brain regions is still required. For example, the prefrontal cortex (PFC) has a control function that can help individuals direct attention to positive stimulation, avoid negative stimulation, and favor processing of positive stimulation by the amygdala. Therefore, we conclude that the amygdala's valence specificity does exist objectively, but is relative. We also need to consider many confounding factors including the materials and subjects, and that complete emotional processing is impossible without bilateral amygdala coordination and synergy of multiple brain regions. Based on the findings and limitations of existing research, we suggest that future research should consider the following: (1) exploring the regulatory effect of attention on the specificity of emotional valence of the amygdala; (2) controlling multiple confounding factors and using more diverse experimental materials such as short videos, instead of being limited to static emotional stimulation; (3) clarifying the connection of brain networks when processing emotional information of different valences, and applying it to clinical practice to explore the feasibility of stimulating the corresponding brain network to regulate emotion and reduce negative emotional experiences of patients with emotional processing difficulties; and (4) exploring the performance of amygdala valence specificity in advanced cognitive processes such as thinking, planning, and decision-making in order to further clarify the neural mechanisms. In this way, future research can break through the limitations of previous studies that used emotional evaluation, attention, and recognition as indicators of results. The discussion on the valence specificity of the amygdala helps us understand the corresponding brain basis of emotional valence and the evolutionary mechanism of positive and negative emotions, in addition to helping us understand the laterality and cooperative relationships of the amygdala in emotional processing. These findings also have multiple implications for psychology and evolutionary epistemology, and can promote research in and development of the field of affective neuroscience.