Based on an analysis on the surface climatological front, the position of 500 mb characteristic contour, the temperature, humidity and flow fields in the lower atmosphere, it is considered that the migratory orientation of the oriental armyworm (Mythimiia, separata walker) agrees with the prevailing wind at 1,500 rri) the northward or southward movement of armyworm flight varies with the seasonal change of the surface climatological front and the average seasonal position of the 500mb characteristic contour...