In recent years, Tiejun, a famous expert in mathematics for postgraduate entrance examination, has become famous in Tianjin, Shenyang, Wuhan, Guangzhou, Shanghai, Xiamen and other big cities. He taught postgraduate mathematics online, and became one of the "Troika" of postgraduate mathematics, which is as famous as Chen Wendeng and Li Yongle. Professor Tiejun has been engaged in postgraduate mathematics. With a strategic, grand, wise and humorous style, he grasped the test sites, key points and difficulties comprehensively, profoundly and thoroughly, cared for students, took a highly responsible attitude, and accurately predicted the test questions, which benefited the candidates a lot.