In the clinical diagnostic process, blood pressure is a crucial parameter that serves as a key reference for assessing blood flow dynamics and health status. Basing photo plethysmo graphy (PPG) for non-invasive continuous blood pressure monitoring has been a surge of interest in the research field, due to the limitations of traditional blood pressure measurements, such as invasiveness and intermittency. Firstly, theoretical background and technical principles of PPG were briefly introduced. Secondly, the specific processes including open datasets, evaluation standards, prepossessing methods, feature extraction, and model establishment, were comprehensively discussed, compared analysis of the advantages and disadvantages of different methods was also conducted. Finally, the challenges and future research directions in achieving non-invasive continuous blood pressure measurement based on PPG were summarized, with the aim of providing guidance for future research endeavors.