Depression is one of the most common clinical psychiatric disorders. With the development of a large number of antidepressants, the treatment of depression is no longer difficult, but the problem of recurrence of depression is still a challenge for the medical community. As the saying goes, “treat the root cause of the disease”, but the cause of depression is not clear. With the increasing understanding of the disease, the cognitive process of depression is biased, which has been confirmed by many studies. Cognition is the information processing activity by which an individual perceives the objective world. Sensory, perceptual, memory, imagination, thinking and other cognitive activities form a certain functional system in accordance with certain relationships, thus realizing the regulatory role of individual cognitive activities. In the process of the individual’s role with the environment, the functional system of individual cognition develops continuously and tends to be perfected. The cognitive processes of depressed patients have their unique aspects and often have cognitive biases. Common cognitive biases in depression: 1. black or white absolute way of thinking, either friend or enemy; 2. generalization or selective generalization, blindness; 3. arbitrary inference, lack of factual basis, hasty conclusion; 4. over exaggeration or reduction; 5. introjected attack, actively taking responsibility for others’ mistakes or misfortunes. And this cognitive bias may be one of the reasons for the constant recurrence or persistence of the condition. The cognitive triad of depression: 1. Negative cognition. Depressed people often see themselves as defective, incompetent or less capable, and abandoned, thus creating a sense of unhappiness and worthlessness, often seeing themselves as superfluous, a liability to their families, and a drag on and affecting the normal lives of others. “A thousand wrongs are my fault”! This is the motto that depressed people are convinced of. 2. Negative interpretation. Depressed people always give negative explanations for everything, believing that failure is to blame and self-inflicted; success is the result of external factors and has nothing to do with their own ability and efforts. Consider the slightly unsuccessful work and unhappy mood are the result of self failure. 3.Negative attitude. The negative cognition of oneself and the negative interpretation of things lead patients to know the world with a negative attitude, to treat people with a negative attitude, and to a future life full of frustration and failure. Cognitive therapists believe that cognition mediates emotions and behaviors, and that negative emotions and maladaptive behaviors are often rooted in poor cognition. Medication for depression is effective, but it does not get to the root of the problem! In patients who are cured, once they encounter a negative life event and pull the trigger, recurrence of the illness may be inevitable. Therefore, patients with depression should receive psychotherapy along with antidepressant medication.