Based on examing the differences of temporal-spatial characteristics of sub-surface sea temperature(ST) among levels over the Northern Pacific by using EOF,SVD,analogical,correlation and composition methods,ST is detached in levels,which is used to study its interactions with sea level pressure(SLP) fields.Evidence suggests that:1)the first mode and its time coefficients can basically reflect the temporal-spatial features of ST over this area;2)ST for January is separated into two levels and that for July into fourlevels,which indicates that the structure in July is more complicated than that in January;3)The temporal characteristics of air-sea interaction is remarkably interdecadal variation,with the "break" taking place in the late 1970s;4)When ST over the central North Pacific is persistently on the high side,the corresponding Aleutian low in January(North Pacific subtropical high in July) is weaker,with lying to the west of the normal position and weaker winter(summer)monsoon,and v.v..