To explore the correlation between the mechanism changes in texture quality of post-harvested commercial bivalve molluscs and the physiological properties changes of muscle protein,a trial study of scallop (Patinopecten yessoensis) edible muscles was carried out focusing on myofibrillar (Mf) protein,and ATPase activities were taken as indicators to explore the stability of myofibrillar protein extracted from adductor (A-Mf) and mantle (M-Mf).Comparisons and analysis between the extracted Mfs from adductor muscle and mantle were made,including the solubility,viscosity,the influences of I,pH and temperature on the ATPase stability of Mfs,and their ATPase inactivation characteristics.The results showed that:(1) A-Mf and M-Mf presented similarity in solubility and both pI appeared around 5.Viscosity analysis showed that the thermal stability of A-Mf was higher than that of M-Mf.(2) Compared with Mg²⁺-ATPase,Ca²⁺-ATPase can more accurately indicate the stability of A-Mf and M-Mf which was the same as vertebrate fishes.(3) The Ca²⁺-ATPase activities of adductor and mantle Mfs had the common characteristics,for example,the highest activity was in the neutral pH;the difference between A-Mf and M-Mf was that the highest Ca²⁺-ATPase activity of the former was at low ionic strength (I=0.2) whereas the latter was at high ionic strength (I=0.5);the influence of ionic strength on the A-Mf was not obvious whereas M-Mf was affected by the ionic strength obviously which showed the better stability at low ionic strength.(4) The inactivation characteristics of Ca²⁺-ATPase showed that both the adductor and mantle Mfs had a significant correlation (R²=0.818 1,0.843 6 and R²= 0.9887,0.9557) with the ionic strength and temperature,the best stability of A-Mf and M-Mf were in the range of pH 7.0,and acid conditions damaged Ca²⁺-ATPase activity more obviously than alkaline conditions.