Abstract: Day-to-day ITCZ set analysed from June-September 850 hPa historic data (1965-1984) at 0000 GMT were used to determine ITCZ’s distribution of occurrence frequency and investigate its climatology and seasonal advancement over the area of the South China Sea and West Pacific, with the result that ITCZ displaces itself northward simultaneously with the Subtropical High and increases its own frequency of occurrence.It is found that ITCZ in the West Pacific tends to take place and stay roughly along 12°N and 20°N, substantiating two belts of high frequency.The bifurcation is closely associated with those for the low-level westerlies and upper easterlies over the equatorial tropics.It is also suggested that the geographical location of ITCZ may be more properly described with the ratio of OLR standard deviation to its average than directly with the minimum axis of OLR.