Abstract: For designing the control and protection system of large-scale AC systems, it is necessary to simulate the electro-magnetic transients of the whole system, especially the high-frequency dynamics aroused by the interactions between individual components. Traditionally, electromagnetic transient（EMT） model and the transient stability（TS） model cannot meet the requirements of the simulation accuracy and efficiency simultaneously. Moreover, they cannot provide the wide frequency-band phasors as required. In order to resolve these issues, this paper proposed a time domain transformation modeling based on the rotational matrix where each component is represented by proposed time domain transformation model. This model can provide instantaneous and wide frequencyband phasors simultaneously. Additionally, the wide frequency-band phasors preserve components of low-frequency and high-frequency. Next, the performance concerning the accuracy and efficiency was compared with the traditional EMT and TS models by simulating a practical AC system, or the China Southern Grid under different scenarios.