The changes of sensory and biochemical characteristics on the fresh and frozen‐thawed scallop adductor muscle during storage at 4°C were discussed in this study. The Quality Index Method (QIM) scheme for evaluating scallop adductor muscle as raw materials for sashimi was proposed for the first time. The results of sensory evaluation showed that frozen‐thawed scallop adductor muscle within zero to one day of refrigeration can be happily accepted by consumers, indicating the superiority of freezing for long‐distance transportation, although the triangle test confirmed that there are still sensorial differences between fresh and frozen‐thawed scallop adductor muscle. The microscopic observation of myofibrils extracted from scallop adductor muscle suggested that the myofibrillar protein which constitutes myofibrils has suffered some extent change due to freezing and thawing, even though the head region of myosin remained stable judging by the fact that there was no significant difference in Ca2+‐ATPase activity (p > 0.05). The changes of adenosine triphosphate (ATP) and its related compounds, and pH value during storage can be regarded as indicators to differentiate fresh and frozen‐thawed scallop adductor muscle. The changes of Mg2+‐ATPase activity indicated that the interaction between myosin and actin was weakened by the freezing and thawing process. Practical Application: The QIM scheme can be used to evaluate the scallop adductor muscle as raw materials for sashimi. The mechanism of quality changes in the frozen‐thawed scallop adductor muscle was discussed in combination with the destruction of myofibrils, ATP degradation and the decrease of pH value. This study has positive significance for improving the quality of frozen‐thawed scallop adductor muscle by combining the changes of sensory and biochemical characteristics.