The present study was performed to investigate the acute toxic effects of mercuric chloride (HgCl_2) and the accumulation concentrations in crucian carp, Carassius auratus as the water temperature changes. The results summarized were as follows. 1. The ranges of acute lethal toxicity for crucian carp were 0.2-2.2㎖/ℓ at water temperature 10℃ and 17℃, and 0.1-2.2㎖/ℓ at water temperature 24℃. 2. The LC_50 values of HgCl_2 were decreased when exposure time of HgCl2 go on increasing. The LC_50 values at water temperature 17℃ were higher than at water temperature 10℃ and 24℃. The LC_50 values at water temperature 10℃ were higher than at water temperature 24℃. 3. The LC_50 values of HgCl_2 for crucian carp during 24, 48, 72 and 96 hour exposures at water temperature 10℃ were 1.11, 1.00, 0.87 and 0.61㎖/ℓ, respectively. The LC_50 values of HgCl_2 for crucian carp during 24, 48, 72 and 96 hour exposures at water temperature 17℃ were 1.43, 1.17, 0.90 and 0.74㎖/ℓ, respectively. And the LC_50 value of HgCl_2 for crucian carp during 24, 48, 72 and 96 hour exposures at water temperature 24℃ were 0.49, 0.37, 0.24 and 0.20㎖/ℓ, respectively. 4. In the 10㎖/ℓ treatment groups, the accumulation concentrations in the muscle of the crucian carp at 24, 48, 72 and 96hour exposure were 0.439, 0.611, 0.815 and 0.99ng/㎎ at water temperature 10℃ and 0.424, 0.548, 0.760 and 0.826ng/㎎ at water temperature 17℃ and 0.455, 0.692, 0.988 and 1.131ng/㎎ at water temperature 24℃, respectively.