Usually, the high-power microwave (HPM) devices suffer from impedance collapse and cathode material degradation or even failure. When the intense electron beam bombards the anode (or named as collector in HPM device), an anode plasma could appear under certain conditions. In this case, the impedance collapse is caused by the expansions of the cathode and anode plasmas and diode current overshot caused by the bipolar flow. In this paper, characterization of a short-pulse high-power diode operated with anode effects with a dielectric fiber (velvet) cathode is discussed. The bipolar flow (or anode plasma) is indeed evident at beam power densities ~11 MW/cm2 and the pulse durations of ~50 ns. The analysis results of the deposit dose and thermal regime of the anode show that the electron stimulated desorption played an important role in the generation of anode plasma in this case. With the effect of anode plasma, the appearance of local cathode plasma flares (or nonuniform electron emission) is particularly detrimental for the diode closure. Micro-structure and elemental surface compositions of cathode are changed by the anode splashing, which is very harmful to the performance of cathode.