The vertical variation and daily change of nutrients and effect of rainwater on seawater nutrients were studied by analysing of sea water nutrients from Nov 1992 to Feb 1993 in the tropical west Pacific, TOGA COARE IOP(4°S156°E). The results showed that dissolved phosphate and silicate increased with depth and that dissolved phosphate minimized at 50m layer Dissolved phosphate and silicate were controlled by discomposition of biological excrement and corpse decomposition under the euphotic layer. NO2-N and NH4-H having inverse distribution tendency showed that they were controlled by inter-transformation of NO2- N and NH4-N. The daily change research showed that mechanism controlling disscoved phosphate is similar to that for silicate during daytime, but is different during nighttime. Phophate and silicate maximized at 4 o'clock, a. m or p. m, and the situation is indefinite under the euphotic layer. Rainwater increased the alkalinity and decreased reduction in the surface layer seawater.NO2 -N could increase 134.86% and PO4-P 6.78%, but SiO3 - Si was almost constant and NH4-N could decrease at the surface layer seawater. The study showed, rainwater could supply N and P to seawater in some degree, and it is one of the important resources of N and P.