The OLR data were applied in this study to detect the low-frequency mode which are pronouced in the equatorial Indian Ocean, and the Western Pacific. 40 day OLR oscillations are closely related to the formation of typyoon. There are some cluster characterists of the typhoon formation not only in spacial but also in temporal distribution. The period when the typhoon frequently occurred was consistent with convec-tive phase of low-frequency mode. This result will be useful to the midium range forecast of the typhoon formation.