In this research, in order to set up the ultimate approaches to determine the content of chromium(¢¾) in seawater, different pH values, the amount of chelating agent, chelating time and extraction time were investigated in two different solvent extraction systems, APDC-MIBK and Aliquat 336-MIBK. In APDC-MIBK system, the ultimate extracting condition is that 400 mL sample is adjusted to pH 3.0, added 4 % APDC 4 mL to chelate chromium(¢¾) for 60 minutes, and added 20 mL MIBK to partiton into two fractions for 5 minutes. The recovery in APDC-MIBK system is 68 %~ 123 %. The method detection limit is 0.2 ppb. In Aliquat 336-MIBK system, the ultimate extracting condition is that 400 mL sample is adjusted to pH 2.0, added 5 % Aliquat 336 4 mL to chelate chromium(¢¾), added 20 mL MIBK to be shaken for 2 minutes, and partitoned into two fractions for 5 minutes. The recovery in Aliquat 336-MIBK system is 80 %~ 120 %. The method detection limit is 0.1ppb. Although in APDC-MIBK system assorted metals can be extracted at same time, it is steadier in Aliquat 336-MIBK system than APDC-MIBK system. Therefore, it is a feasible extraction method to adopt Aliquat 336-MIBK system to determine the content of chromium(¢¾) in seawater.