Some efforts were made to measure the electron emission characteristics of velvet under multi-pulse mode. The voltages across the diode were 1 MV for two-pulse mode and 500 kV for four-pulse mode. Pulse duration was 100 ns and pulse to pulse separation was 400 ns. The research indicates that under multi-pulse mode the emission of velvet is not uniform and that beam degradation is caused by cathode plasma motion. The factors that determine the plasma motion are analyzed and the experimental results of plasma velocity and its distribution are presented. (c) 2005 Elsevier B.V. All rights reserved.