Delphi method mainly means that investigators draw up questionnaires according to established procedures and seek the opinions of expert group members by letter; Members of the expert group submit their opinions anonymously (by letter). After several times of repeated consultation and feedback, the opinions of the members of the expert group gradually tended to be concentrated, and finally a collective judgment result with high accuracy was obtained. Therefore, no expert signature is required.

Delphi method, also known as expert investigation method, was initiated and implemented by RAND Corporation of the United States in 1946. Its essence is an anonymous feedback query method. Its general process is to sort out, summarize and count the problems to be predicted after obtaining the opinions of experts, and then give anonymous feedback to the experts, solicit opinions again, concentrate again and give feedback again until unanimous opinions are obtained.