Physiological studies on the salinity tolerance with respect to survival rate and body composition changes of the abalone Haliotis discus hannai were conducted by rapidly changing the salinity in an indoor rearing system. The survival rate of the control (35 psu), 30 and 25 psu groups at $15^{circ}C$ was 100%. The survival rate of the 20 psu group was $35{pm}5.0%$. Survival rate of the 15 psu group was 0%. At $15^{circ}C$ and 35, 30, 25, 20, 15 psu, the moisture contents of abalone muscle were $82.1{pm}0.7$, $82.5{pm}0.7$, $84.9{pm}0.5$, $86.9{pm}0.3$ and $86.6{pm}0.4%$, respectively. Crude lipid contents were $0.47{pm}0.03$, $0.47{pm}0.03$, $0.47{pm}0.09$, $0.77{pm}0.09$ and $0.63{pm}0.03%$, respectively and crude ash contents were $1.30{pm}0.12$, $1.33{pm}0.15$, $1.13{pm}0.23$, $1.87{pm}0.15$ and $1.40{pm}0.31%$, respectively. At salinity below 20 psu, these values increased compared with the control. The general components of abalone muscles significantly increased below 20 psu, while amino acid composition showed no significant difference with salinity and water temperature.