The characteristics of X-ray emission in aluminum plasmas using 45 fs and 6 ns pulsed lasers respectively are reported. It shows that under the fs laser, the X-ray emission is dominantly from the K shell, the aluminum plasma′s temperature is 500 eV and the electron density is 3×1021/cm3, while under the ns laser, the L shell, 100eV and 2×1020/cm3 are obtained correspondingly. The spatial distributions are also compared simply.