The invention discloses a quantitative assessment system for depression degree, which comprises: an integrated detection device for electrocardiogram and pulse wave, a data transmission device, and a data processing platform. The invention also discloses a method for quantifying, evaluating and diagnosing the degree of depression, which includes the following steps: step 1, obtaining the physiological information of the human body in different states through a multi-state comprehensive test platform; HRV characteristic parameters; step 3, evaluating the balance state of sympathetic and vagus nerve functions in the autonomic nervous system; step 4, establishing a quantitative evaluation model of depression degree to realize rapid and objective evaluation of the degree of depression of the subject. The invention belongs to the technical field of computer-aided diagnosis, realizes the quantitative evaluation of depression degree, fills the gap in the technical field of depression examination, is simple and easy to implement, saves medical resources, and has good clinical practicability.