To clarify the effect of life or death condition before cooling on the physicochemical properties of plaice, Paralichthys olivaceus muscle at the early period after death, the plaices were dipped in the refrigerated sea water ($0^{circ}C$) either as alive or after anesthesia killing. These samples were stored at $0^{circ}C$ sea water and the changes in rigor-mortis, ATP breakdown, content of ATP and its related compounds, breaking strength and lactate accumulation through storage were investigated. Acceleration of rigor-mortis, ATP breakdown and lactate accumulation were taster in the samples refrigerated as alive than in samples killed by anesthesia before cooling. ATP in samples refrigerated as alive showed little breakdown until 7.5 hrs but it was decomposed completely after 17.5 hrs storage. The breaking strength in muscle of plaice was 1736.2 $pm$ 65.4 g immediately after killing. The breaking strength in samples dipped in refrigerated sea water as alive increased more rapidly and showed the maximum value over 7.5 hrs (2183.3$pm$32.2 g), However, in case of samples killed by anesthesia before cooling, the value and time reached around the maximum breaking strength were 2126.3 $pm$ 32.2 g and 12.5 hrs, respectively and then decreased until 30 hrs. From these results, it could be suggested that dipping in refrigerated sea water after anesthesia killing before cooling is more effective in maintaining freshness of fresh plaice muscle than refrigerating as alive.