According to the latest experimental results of HPM effect on digital electronic devices, a relation between the HPM pulsewidth(PW) and the upset threshold(UT) of effect obiect is sumaried. The relation suggests that UT decreases with the increasing of PW as the other factors are fixed, wheras, there is a inflection region of UT while PW increasing. The UT changes slowly when the injecting PW is greater than the PW corresponding to the inflection region.