Via the auxiliary differential equation method, the authors propose a simple and efficient implementation of the stretched coordinate perfectly matched layer (SC-PML) in this Letter. The proposal can successfully halve the number of auxiliary variables associated with the PML while maintaining the capacity of the original SC-PML in terms of simple implementation. Thus, it can achieve a higher computational efficiency in the finite-difference time-domain simulations. The effectiveness of this new implementation is verified through an example carried out in a 3D Debye dispersive space.