A scheme of high-accuracy time-synchronization between a shaped optical pulse and a probe optical pulse has been developed and used in the Shenguang Ⅱ facility. In this scheme, the probe optical pulse is firstly photoelectrically converted by the Si photoconductive switch and then used to trigger the laser pulse-shaping subsystem, so that laser pulse-shaping subsystem produces a shaped optical pulse synchronized with the probe optical pulse. In order to decrease time jitter induced by amplitude fluctuation of the triggering signal, the probe optical pulse is amplified to adjust amplitude of the triggering signal before photoelectric conversion. The synchronization root-mean-error less than 4.5 ps between the two pulses has been achieved with this scheme.