The correlation analysis between the sea temperaturn of the Pacific Ocean and the Holiothis Armigera Hübner generation degree was made, 12 correlation fields were established,2 favourable areas were obtained. The forecast equations were given by use of the principal component analysis and forecast variables. The preper forecast can be made 2 to 3 months in advance. The opera-tionnal forecast from 1993 to 1995 was proved to be coincident with the actual situation.