Rapid electrical heating is an effective method for the efficient heat treatment of metallic materials, offering high production efficiency and process flexibility. Compared with conventional heat treatment, rapid electrical heating—driven by the synergistic effects of Joule heating and non-thermal mechanisms—can achieve rapid phase transformation and microstructural refinement within an extremely short time, while effectively suppressing grain coarsening, thereby significantly altering the kinetics of microstructural evolution. However, this process involves multiple adjustable parameters, and current industrial production largely relies on the empirical experience of operators, lacking systematic studies and theoretical support for process optimization. Herein, TC4 alloy bars were subjected to rapid electrical heating up to various heating temperatures and holding for different times, in terms of the effect of process parameters on their microstructural evolution. The results indicate that both the size and volume fraction of the β-transformed microstructure increase with the rising temperature of electrical heating and the prolonging hold time. When the holding time is short or the heating temperature is relatively low, the average grain size first decreases and then increases with increasing temperature or holding time. By longer holding times or higher heating temperatures, the grain size increases monotonically with temperature or holding time. Compared with conventional heat treatment, these microstructural evolution behaviors occur within an extremely short duration, highlighting the unique efficiency of rapid electrical heating in microstructure control. This study elucidates the characteristics and mechanisms of microstructural evolution of TC4 alloy by rapid electrical heating. The findings may provide a reference for process optimization and performance tailoring for metallic materials.