The chemical properties of water masses were investigated at 33 stations of the southeastern last Sea in February, 1995 on board R/V Tam-Yang. The water masses were not clearly distinguished due to the vortical mixing in winter. However, on the basis of the T-S and $T-O_2$ diagrams, water masses in the study area were divided into five groups (Type I, Type II, Type III, Type IV, Type V). (1) $>9.0^{circ}C,;>34.35;psu,;5.08~5.60mell/ell$ at Type I, (2) $6.0~9.0^{circ}C,;34.15~34.35;psu,;5.60~5.90;mell/ell$ at Type II, (3) $4.0~6.0^{circ}C,;34.00~34.15;psu,;>5.90mell/ell$ at Type III, (4) $1.5~4.0^{circ}C,;34.00~34.05;psu,;5.40~5.90;mell/ell$ at Type IV, (5) $<1.5^{circ}C,;34.05~34.07;psu,;4.80~5.40;mell/ell$ at Type V. In the vertical profiles of nutrients, the concentrations were very low in the surface layer and increased rapidly with depth. The highest concentrations occurred in Type IV, while the concentrations in Type I were the lowest. The N/P ratios were less than Redfield ratio, indicating that nitrogenous nutrients were the limiting factor tor phytoplankton growth. The concentrations of POC and PON were in the range of $0.49~20.03;{mu}g-at/ell;and;0.09~5.34;{mu}g-at/ell$, respectively. The relatively high concentration occured in the surface layer of inner shore, showing that the concentration at each water mass followed the order Type I > Type II > Type III > Type IV > Type V, respectively. The C:N ratio in particulate organic matter was lower than the values reported in other region due to relatively high concentrations of PON in the study area. Relatively high ratios of POC to chlorophyll $alpha$ during the study periods indicate that non-living detritus comparised most of the POC in the study area.