  The attosecond streaking technique is normally utilized to characterize the
attosecond pulses in extreme ultraviolet spectrum, while the pulse simulation
and reconstruction schemes turn out to be unreliable for extremely short
sub-100as pulses. Based on systematical analysis and subtle investigation, we
developed a dynamic streaking model for ultrashort photoelectron pulses and
demonstrated concretely how the temporal phase of attosecond pulses would
influence the streaked spectrogram. Upon that, a novel numeric scheme is
established to retrieve the pulse-lengths and chirps. Different with the
traditional FROG-CRAB algorithm utilizing the central energy approximation, our
approach concerns the actual time-energy distribution of an electron
wave-packet within sub-100as time-scale, capable for retrieving the temporal
profiles of the ultrashort pulse more accurately.
