Impact detecting and counting are fundamental functions of fuses used in hard target penetration weapons. However, detection failure caused by battery breakdown in high-g acceleration environments poses a vulnerability for such weapons. This paper introduces a novel supercapacitor that combines energy storage and high-g impact detection, called self-sensing supercapacitor. By deliberately inducing a transient soft short-circuit during shock in the supercapacitor, it is possible to detect external impact by its transient voltage drop. To realize this concept, firstly, by introducing the contact theory and force-induced percolation model, the electrode strength and roughness are found to have key impacts on the formation of soft circuits. Subsequently, to meet the needs for sensitivity and capacity, a high-density porous carbon (HDPC) that combines high mechanical strength and porosity, is selected as a suitable candidate based on the analysis results. Furthermore, a two-step curing method is proposed to prepare the high-roughness HDPC (HRHDPC) electrode and to assemble the self-sensing supercapacitor. Due to the rich specific surface of the electrodes and the high surface strength and roughness conducive to the formation of transient soft short circuits, the self-sensing supercapacitor not only possesses an excellent specific capacitance (171 F/g at 0.5 A/g) but also generates significant voltage response signals when subjected to high-g impacts ranging from 8000g to 31,000g. Finally, the self-sensing supercapacitor is applied to compose a successive high-g impact counting system and compared to traditional solutions (sensors and tantalum capacitors) in the military fuzes. The results show that the self-sensing supercapacitor-based system exhibits advantages in terms of size, power consumption, and counting accuracy.