Tilapia was used as material to extract myosin. The effects of heat treatment (40-80 ℃, 1℃/min) on the turbidity, solubility, surface hydrophobicity, α-helix contentand aggregated particles of myosin were investigated underdifferent ionic strength (1,50,150,300,600 mmol/KCl).The results showed that the ionic strength and heat treatment significantly affected the thermal denaturation and aggregation of myosin. Myosin has poor solubility because of it assembles and forms a filamentous polymer under low ionic strength (1-150 mmol/L KCl), after heat treatment, the molecular aggregation precipitates, the solubility and α-helix content decreased (p<0.05), the thermal stability of the myosin in this system was undesirable. Whileunder the high ionic strength (300-600mmol/L KCl), myosin dissociated into monomer,the solution is clear.When the temperature is higher than 50 ℃, a increase in turbidity and decrease in solubility of tilapia myosin was detected, accompanied by increasing in surface hydrophobicity and a significant loss of α-helix (p<0.05), but the molecular aggregation is not obvious.The results indicated that the electrostatic shielding of high salt ions inhibited formation of myosin filament, which also protects the molecular structure of myosin.So that the myosin that under the high ionic strength has better stability.