Abstract: Converter transformers exhibit complex differential current characteristics under conditions such as excitation inrush current and internal faults. Traditional methods based on current amplitude or harmonic characteristics are difficult to explain the differences in current response under different operating states from a mechanistic perspective. In response to this issue, the article establishes a mapping relationship model between magnetic flux and differential current based on magnetization characteristics, and analyzes the changing characteristics of this relationship under different operating conditions, aiming to provide reference for transformer state evaluation and feature extraction based on magnetization mechanism.