In order to estimate acute toxicity of various heavy metals on mysid, Neomysis japonica, the experiments were conducted by renewal bioassay method at $20pm0.5^{circ}C$ and $30pm0.3$ psu salinity. The 96 hr $LC_{50}$ of Neomysis japonica exposed to cadmium, copper, zinc, arsenic, lead and chromium were $90.4;{mu}g/L$, $82.3;{mu}g/L$, $646.1;{mu}g/L$, $1488.5;{mu}g/L$, $1758.8;{mu}g/L$ and $1609.6;{mu}g/L$, respectively, and were ranked in order of toxicity: copper > cadmium > zinc > arsenic > chromium > lead.