Debugging of parallel programs suffers from the existence of race condition,timing error, deadlock and nondeterminancy. EVTPD (event -based visualization techniques on parallel debugging) provides a way to solve these problems. Event monitoring and visualized replay are the two basis of EVTPD. In this paper, the following key techniques are discussed: event description, event filtering, event recognition, time stamping,trace replay, execution replay and view definition. As an example, a parallel debugger is designed for workstation cluster.