Studied, the inhibitory effect of DS on thermal aggregation of tilapia myosin (2.0 mg/mL) in low ionic strength (1, 50, 150 mmol/L KCl) during the heat treatment (40～80 ℃, 1 ℃/min). The result showed that the myosin had poor solubility in 1 mmol/L KCl. While, with the icreased of ionic strengths, myosin fibrils could dissociate in 50 and 150 mmol/L KCl. After heating, the myosin filaments disappeared, and the heads and tails of myosin aggregated seriously, resulting in the solubility and the content of α-helix decreased significantly. After adding 0.4 mg/mL DS, the change of turbidity, solubility and α-helix content was not obvious in the range of 40～80 ℃. Compared to the samples without DS, the solubility, ζ-potential were higher at the same temperature (P＜0.05). The results suggested that the strong electrostatic interaction between DS and myosin can effectively inhibit the thermal denaturation of myosin under low ionic strength.