To separate the aging oil emulsions on offshore platforms, a series of polyether demulsifiers based on proanthocyanidins were synthesized, and a dehydration ratio of 94.4% can be obtained at a dosage of 100 mg/L and 70 degrees C within 120 min. The exceptional performance is due to the multibranched structure and multiaromatic core of the demulsifier, as revealed in our previous work. Meanwhile, the moderate molecular weight, high hydrophilicity, and high interfacial activity of the demulsifier also improve its performance. To understand the distribution of the demulsifier molecules after demulsification and elucidate the demulsification mechanism, partition coefficient (K-pc) measurements were performed using the fluorescence labeling method. The results demonstrate that the demulsifier molecules are mainly present in the oil phase and the high K-pc values favor demulsification. Furthermore, a high dehydration ratio can be achieved when the demulsifier has a strong ability to reduce the elastic modulus of aging oil emulsions, as illustrated by the rheological results. To confirm the practical applicability of the demulsifiers on offshore platforms, pilot production on a ton scale was carried out and the pilot product was found to exhibit excellent performance that was essentially the same as that of the laboratory sample.