Pre-ablation double-pulse (DP) is applied to induce Fe plasmas, and the emission spectrum is investigated. Spectra intensities are compared using single-pulse laser-induced breakdown spectroscopy (SP-LIBS) and pre-ablation double-pulse laser-induced breakdown spectroscopy (DP-LIBS). The signal intensity is enhanced largely by pre-ablation DP-LIBS excitation compared to SP-LIBS. Signal enhancement acts as object of study. The influence of the delay between the two laser pulses (-102~0 μs) is investigated, and enhancement reaches maximum at -9 μs, and 6.5 times enhanced signal is observed in atomic line. Electron density is reflected by spectral line of full width at half maximum (FWHM). FWHM is studied with the delay between the two laser pulses and the gate delay time. A correlation between the increases in emission lines intensities and the gate delay time is established in pre-ablation DP approach. Difference of the delay between the two laser pulses, intensity enhancement versus the gate delay time is different.