What is a "fan"? There is such a group of ordinary people in the world, they love their idols more than their loved ones, love themselves, they are crazy about their favorite stars, spending money, energy and even risk their lives, these people are collectively known as "fans" (English fans). What is a fan? It is a kind of position, an attitude, a kind of "love" for the idol and pay regardless of the cost. Nowadays, fans are mostly working children born in the 70's and 80's, who have the mentality of fashion and popularity, and have become the main body of fans in today's society. 2005, after the Supergirl, fans were transformed from stargazers and spread all over the world. Fans have become a huge group of people that sociologists have to look at squarely. Fans are no longer just a phenomenon, but have gradually formed into a "fan culture" with unique and distinctive characteristics. Fan culture is not only used in popular culture, but also in science, politics, religion and other fields that require a high degree of rationality. The birth of fan culture departs from rationality and begins the transformation of idols, society and history.