Plasma of steel sample is produced by single and reheating double pulses laser-induced breakdown spectroscopy in air, and the spectrum excited by two ways is studied. Two lasers are used in reheating double pulses laser-induced breakdown spectroscopy. One arm is used to ablate samples to produce plasma; while the other arm is reheat to the produced plasma. Through comparison of reheating double pulses and single laser on steel sample show that intensity of emission spectrum is enhanced; signal of continuous spectrum is amplified; Signal repeatability is improved using reheating double pulses excitation, the measured signal relative standard deviation is decreased from 5.0% to 2.0% by ten times. In addition, the factor affecting signal enhancement is presented and discussed. The signal enhancement level with the delay between two pulses and the acquisition delay are also investigated. At the same time, an additional research issue to be tackled is the effect of the increasing influenced by excitation energy levels. The higher the excitation energy levels are, the more the enhancements are.