In order to study the effect of different pH value on the thermal aggregation behavior of myosin， the purified pork myosin was used as the research object. Under the pH value of 5.5， 6， 6.5， 7， 7.5， 8， 8.5， the dynamic light scattering， differential fluorescence scanner， negative dye transmission electron microscopy were used. The results showed that the pH increased from 5.5 to 8.5， the denaturation temperature of protein decreased from 40.2 ℃ to 36.9 ℃， the inactivation temperature of Ca2+- ATPase increased from 40 ℃ to 60 ℃， and the degree of cross-linking between protein aggregates increased significantly. Under the condition of pH 5.5， the aggregate structure is relatively loose， forming granular aggregate. With the increase of pH value， the protein denatured， the structure fully expanded， the exposure of hydrophobic groups was high， the hydrophobic interaction between molecules was strong， and the molecules gathered orderly. This study elucidated the formation mechanism of thermal aggregation of pork myosin， provided a theoretical basis for the analysis of other fibrous protein aggregation mechanisms， and had important practical significance for guiding the industrial production of meat products.