Abstract: In this paper, a microsecond-pulse generator with a rise time of about 0.5 s, a pulse width of about 6 s and an amplitude of up to 40 kV, and a nanosecond-pulse generator with a rise time of about 150 ns, a pulse width of about 300 ns and an amplitude of 50 kV, were used to produce diffuse discharges at atmospheric pressure. A saw-blade and a knife blade were used as the electrodes. Characteristics of diffuse discharges under different conditions, in different cases of the applied voltage, pulse repetition frequency (PRF), anode structure and gap distances, were investigated by analyzing the voltage-current waveforms and discharge images. The experimental results showed that both microsecond-pulse and nanosecond-pulse power supplies could generate large-area diffuse discharges, and the maximum area reached 90 cm2. The uniformity of diffuse discharges were significantly affected by the pulse parameters and anode structure. The best homogeneity could be obtained in the case of a knife blade when nanosecond-pulse generator was used. Furthermore, under the same conditions, the instantaneous power for nanosecond-pulse discharges was larger than that for microsecond pulse discharges, and the largest instantaneous power was 275 kW. However, the energy for nanosecond-pulse discharges was smaller than that for microsecond pulse discharges. In addition, other things being equal, the conduction current decreased with the increase of the gap distance, the discharge intensity increased with the PRF, and the working range of the applied voltage significantly decreased with the PRF. Therefore, its most likely to obtain homogeneous diffuse discharges with wide range of working voltages in atmospheric pressure air when the knife blade electrode was used as the anode at low PRF.