In the pulsed electroacoustic (PEA) space charge measurement system used for coaxial cables, the waveform of a coupled pulse will directly affect space charge profiles in cable insulation. In this paper, on the basis of the PEA measurement system with pulse injection from a measuring electrode, the original charge acoustic signals in a 35 kV cross-linked polyethylene (XLPE) cable were collected directly from the oscilloscope under different ground distances between the measuring point and the ground point along a cable’s semiconductive (SC) layer. At the same time, the effects of ground distance, cable specification, and cable length on the waveform of a coupled pulse were studied through a series of experiments and simulations. The results show that the amplitude of the coupled pulse is directly proportional to the ground distance but inversely proportional to the cable cross section or voltage class. Furthermore, the pulse coupling efficiency is almost the same only if the cables have the same diameter of the outer SC layer. Therefore, a constant pulse coupling efficiency can be obtained by adjusting the ground distance according to the diameter of the cable’s outer SC layer.