SUN Zhengjun was born in 1982 in Taizhou, Jiangsu Province. He is an associate professor of School of History, Capital Normal University. From 2000 to 2010, his attended Department of History at Peking University, during which he obtained his BA and PhD degree of history and had an exchange program to Kyoto University, Japan. From 2010 to 2012, he worked in the postdoctoral research station of School of Humanities, Tsinghua University. He is mainly engaged in researches on the bureaucracy history of Han to Tang Dynasty and critical studies of historical documents.