A method for evaluating systolic and diastolic blood pressures of a subject for a blood pressure detecting system is disclosed. The blood pressure detecting system includes a processing module and an image capturing module configured to continuously records a hand and a face of a subject to retrieve multiple hand and face images associated with the subject. The method includes, by the processing module, obtaining biological information related to blood pressure of the subject according to the multiple hand and face images retrieved by the image capturing module； and, by the processing module, obtaining prediction results of systolic and diastolic blood pressures of the subject according to the biological information related to blood pressure of the subject.
