We have made some experiments to study the emission performance of velvet cathodes with long (120ns, 50ns) and short (3ns) pulses. The cathode current densities are 400 kA/cm2 and 7kA/cm2 respectively. The voltage-current plot, cathode emission pattern, scanned electron microphotograph and the practical construction of velvet cathodes are presented. Some ideas about emission mechanism of velvet cathodes have been suggested.