To reveal the mechanism of Qinchuan beef color change during postmortem storage， the pH， meat color and relative myoglobin content was measured in the longissimus dorsi muscle of 25-month-old cattle at 0， 4 and 8 d. The relationship between changes in protein expression of oxidative phosphorylation metabolic pathway and changes in myoglobin expression during storage was investigated based on 4D-unlabeled proteomics technology. The results showed that the pH value decreased and then slightly increased， the a* value decreased， the b* value increased， the L* value increased and then decreased， the relative content of oxymyoglobin decreased significantly (P < 0.05)， the relative content of metmyoglobin increased significantly (P < 0.05)， and the relative content of deoxymyoglobin did not change significantly with the storage time. Myoglobin expression was upregulated from 0 to 4 d and downregulated from 4 d to 8 d， with an overall downregulation trend. The key proteins on the oxidative phosphorylation metabolic pathway， ATP5F1D， were up-regulated at the beginning of storage and down-regulated at the end of storage for NDUFA4 and NDUFB5， and the key proteins on the oxidative phosphorylation metabolic pathway had significant effects on pH and meat color of the longissimus dorsi muscle； L* values were highly significantly positively correlated with the relative content of DeoMb (P < 0.01)， highly significantly negatively correlated with the relative content of OxyMb (P < 0.01)， and highly significantly correlated with ATP5F1D (P < 0.01)； NDUFA5 was significantly and negatively correlated with the relative content of metmyoglobin (P < 0.05). Therefore， investigating the effect of key proteins of the oxidative phosphorylation metabolic pathway on meat color has an important regulatory role in post-slaughter meat quality formation.