Abstract: The occurrence of sweetpotato weevil Cylas formicarius in Chongqing was investigated during 2011 and 2012 in Wushan county, Chongqing for understanding the occurrence characteristics. The larvae, pupae and adults of sweetpotato weevil in tuberous root could overwinter in storage or in open field. The sweetpotato weevil occurred seriously in nursery bed. Therefore, the control of sweetpotato weevil in nursery bed was very important. The damage of sweetpotato weevil was more serious in the field of monoplanting sweetpotato than sweetpotato interplanting with corn. The peak period of adult occurrence was from beginning of August to October. The different generation of weevils was not distinct. The causes of sweetpotato weevil outbreak were its high fecundity, optimum temperature for overwinter and sustain food source in Chongqing area.