1986–1989, Lecturer, Department of Epidemiology, Henan Medical University, Zhengzhou, Henan, China.

1992–2001, Associate Professor,Vice-director,Department of Epidemiology，College of Public Health, Henan Medical University, Zhengzhou, Henan, China.

2004–present, Professor，Department of Epidemiology and Statistics College of Public Health Zhengzhou University, Zhengzhou, Henan, China. Director of Henan Cancer Epidemiology Key Lab.

2008-2009，Visiting Professor, Cancer Epidemiology Lab,Department of Biological Sciences. University of Texas at El Paso