Denaturation of actomyosin from the obliquely striated mantle muscle of squids (Todarodes pacificus) was studied by measuring the changes in $Ca^{2+}$-ATPase activity, relative viscosity, and solubility during frozen storage at three different temperature zones of maximum ice crystal formation $(-3^{circ}C,;-;-5^{circ}C)$, the eutectic point $(-11^{circ}C)$, and $-20^{circ}C$. The logarithms of $Ca^{2+}$-ATPase activity, relative viscosity and solubility of the actomyosin solutions (0.6 M KCl) and suspensions (0.05 M KCl) tended to decrease during frozen storage. The denaturation of squid actomyosin at the zone of maximum ice crystal formation significantly differed by only two degree of temperature difference between $-3^{circ}C$ and $-5^{circ}C$, and it (0.05 M KCl) at $-3^{circ}C$ was less than those of other temperature. The denaturation at $-11^{circ}C$ was more rapid than at $-5^{circ}C$. The logarithms of $Ca^{2+}$ -ATPase activity, relative viscosity, and solubility were changed slower in the suspensions (0.05 M KCl) than the solutions (0.6 M KCl) at all experimental temperatures.