Major depressive disorder is a common mood disorder. The latest treatment guidelines have pointed out that comprehensive intervention based on assessment should be taken in the whole course of the disease. It is found that how people use smart phones can reflect their emotion， language， and social interaction related to depressive activity and severity. Thus smart phone usage behavior has the potential to be an objective evaluation indicator of depression. By collecting the smart phone usage behaviors of relevant people in their daily life environment， this paper hopes to find behavioral indicators that can reflect the severity of depression symptoms， and provide a basis for the establishment of an objective indicator system for the assessment of depression symptoms in the future.