To avoid the impact of the transient saturation of a current transformer, a fast busbar protection method based on the initial traveling wave integrated active power differential principle is proposed in this paper. The Peterson equivalent model is applied to analyze the initial traveling wave distribution characteristics of the internal and external faults of the busbar. The initial traveling wave active powers of each sampling point on each transmission line connected to the busbar are calculated with the implementation of an S-transform. By introducing the integrated active power actuating quantity and active power braking quantity, a protection criterion with a characteristic braking ratio is proposed. The theoretical analysis and experimental simulation results show that the protection performance is sensitive and reliable, with a quick response and simple criterion, and is essentially not susceptible to the impacts of the initial fault angle, fault type, and fault resistance.