The role of photoplethysmography (PPG) in the functional assessment of the cardiovascular system at home and abroad was summarized to provide theoretical references and lessons for the medical application of PPG and innovative research. Currently, functional assessment indices such as heart rate, heart rhythm, blood pressure, and volume can be analyzed from PPG signals, which can also assist in identifying and diagnosing abnormal blood pressure, diabetes mellitus, cardiac arrhythmia, sleep apnea syndrome, early ischemic shock, and other diseases. However, the accuracy and precision of PPG, data interpretation and standardization, waveform analysis, and clinical applications remain controversial. PPG has been widely used in medical and scientific research to effectively assess the functional status of the cardiovascular system and assist in diagnosing various diseases. In the future, PPG is expected to show a multipath development trend in high-precision, multi-parameter, noncontact, remote monitoring, and medical treatment.