Abstract: The single event transient（SET）effects of optocoupler HCPL-5231 and HP6N134 were qualitatively investigated with single event effects simulation by pulsed laser test facility. The relation between transient pulse shape and pulsed laser equivalent LET was tested. The amplitude and duration of transients of both devices are increasing as equivalent LET raises. Then the sensitive areas of the SET effects were identified and the mechanism was initially analyzed. The relation between optocoupler SET width and equivalent LET value was tested by pulsed laser. And the SET cross-section was measured with automatical scanning by laser test facility. The cross-section results of optocoupler for HCPL-5231 are in good agreement with heavy ion data.