Abstract: Nano-copper electric pulse sintering is a kind of rapid chip packaging technology, which has the advantages of high strength, high temperature resistance and low energy consumption. This new packaging process has broad prospects, whereas, the existing researches mainly focus on application optimization and the physical mechanism of instantaneous sintering process is rarely explored. With the aid of high-speed photography, shear test, scanning electron microscope and so on, the time-varying characteristic of resistance of nano-copper sintering sample is researched in this paper. The results show that there is a clearly inverse relationship between sample resistance and shear strength, and the lower the sample resistance is, the higher the shear strength will be. During the first pulse discharge, the resistance mainly depends on the bond of nano-copper particles, which decreases at first and then stabilizes with time. During the subsequent pulse, the resistance rises and the rising rate slows down with time, which is affected by the Joule heating effect. Moreover, there is an optimal number of discharges for pulse sintering. At first, the solder layer becomes denser with the increase of number of discharges, which results in the resistance's decrease and the increase of shear strength. When the number of discharges exceeds the optimal value, the solder layer seems to deteriorate with the increase of discharges number then the resistance rises and shear strength reduces. At last, a calculation model of sample resistance is proposed, which can accurately predict the time-varying characteristics of resistance under electric pulses.