Qualitative evidence synthesis(QES) mainly includes qualitative research in a certain subject area.It is a systematic review of processing narrative data.This paper expounds the definition,advantages and disadvantages,common methods,updating,and relationship between qualitative evidence synthesis and quantitative evidence synthesis,as well as the application of QES in medical field.In the field of medicine,QES can provide evidence for the development of policies and guidelines,describe the experiences of health care participants,explore how different stakeholders and groups evaluate different outcomes,and assess the acceptability and feasibility of interventions.