By adopting double pulses and single pulse laser, laser induced experiments were done for carbon of standard iron alloy samples in the air, and the spectrum obtained in those experiments were compared. Double pulses laser induced breakdown spectroscopy uses two laser beams. On the basis of the first laser pulse, a second laser pulse with high voltage was added, and secondary excitation was carried out for plasma. The comparison results show that double pulse excitation technique can extend the effective time of the feature atomic radiation, improve the SNR of the signal, enhance the signal strength of the emission spectrum, and improve the stability of the signal. In addition, by analyzing the factors that influence the extent of enhancement of the double pulses signal, the influence of the pulse width, delay time, and the excitation stage on enhancement extent of spectrum is also studied.