As an advanced discharge technique, the High Power Impulse Magnetron Sputtering (HiPIMS) has the advantage of high density and high ionization degree plasma, which is widely applied in the surface engineering. However, systematic investigations into the intrinsic correlation between discharge parameters and the resulting plasma characteristics remain scarce. As an extremely important parameter, the pulse duration can affect the discharge current, plasma dynamics and ultimately the microstructure of deposited films. Recently, we have found that the peak amplitude of discharge current can strongly increase as the pulse duration becomes shorter, while the underlying physical mechanism remains elusive. In this work, to elucidate the effects of pulse duration on gas breakdown, self-sputtering behavior, and afterglow plasma dynamics, a comprehensive study combining high-time-resolution diagnostics and numerical simulation was conducted. The experiments were performed on a Ti target using a custom HiPIMS power supply, operating at fixed voltages of －600 V and －800 V, a pulse frequency of 500 Hz, and pulse durations ranging from 100 to 200 µs. Key plasma parameters were diagnosed via a Langmuir probe and Optical Emission Spectroscopy (OES), complemented by numerical simulations using the Ionization Region Model (IRM). Experimental results demonstrate that shortening the pulse duration from 200 µs to 100 µs leads to a substantial increase in the peak discharge current from ～65 A to ～154 A, accompanied by a nearly twofold increase in ion density (from ～3×10¹⁹ m^-3 to ～6.5×10¹⁹ m^-3). Langmuir probe measurements confirmed that more high-temperature electrons are present in the early phase of short-pulse discharges, which favors enhanced ionization. IRM simulation results further uncovered the core mechanism: short-pulse sustains a significantly higher residual Ti atom density in the afterglow phase. Benefiting from their lower ionization energy and higher ionization coefficient compared to Ar atoms, these residual Ti atoms facilitate a more intense electron avalanche at the inception of the subsequent pulse. This triggers a positive feedback loop of ionization and sputtering, thereby drastically boosting the initial ionization rate and peak discharge current. This work clarifies the intrinsic physical mechanism behind the peak current enhancement in short-pulse HiPIMS and provides a reference for deepening the understanding of HiPIMS plasma dynamic characteristics and regulating high-performance coating preparation processes.