We elaborated the reasons why systematic reviews need to use GRADE based on a couple of specific examples. Aiming to provide references to understand and use GRADE correctly, we also answered some frequently-asked questions and concerns about GRADE as follows: a) differentiating the uses of GRADE between its application in guidelines and in systematic reviews; b) how to determine the overall quality of evidence? c) can GRADE be used to access the quality of single study or not? d) different uses of GRADE between randomized controlled trials (RCTs) and observational studies; e) weight of GRADE items; and f) factors that might influence the results of GRADE and the balance between upgrading and downgrading.