The dynamic of population emergence and the applied measurements of forecast and control of oriental armyworm Mythimna separata（Walker）in Jilin province in resent 20years were expounded on this paper based on some information from field survey in the emergence periods,the data of lure trap catches in every spring,and the outbreak and damage records of the first and second generations of oriental armyworm in Jilin province.The technological proposals on forecast and control of oriental armyworm were put forward.