  We have observed the largest optical spectra sample of 74 blue compact
galaxies. Stellar population properties of them were derived by comparing the
equivalent widths of strong absorption features and continuum colors, using a
method of empirical population synthesis based on star cluster sample. The
results indicate that blue compact galaxies are typically age-composite stellar
system, the continuum flux fractions at 5870\AA due to old stellar components
and young stellar components are both important for most of the galaxies. The
stellar populations of blue compact galaxies present a variety of
characteristics, and the contribution from different age and metallicity
components is different. The star formation episodes are usually short, some
galaxies maybe undergoing their first global episode of star formation, while
for the most sample galaxies, older stars contribute to at most half the
optical emission. Our results suggest that BCGs are old galaxies, in which star
formation occurs in short intense burst separated by long quiescent phases.
