We examine the dynamic behavior of sodium (Na) release during the pulverized coal combustion of Zhundong lignite using a laminar, Hencken flat-flame burner technique. By subtly utilizing the gap between the excitation energies of the gas and particle phases, a new low-intensity laser-induced breakdown spectroscopy (LIBS) is developed to distinguish the sodium existences in the particle or gas phases along the combustion process. Within the coal flame domain, the Na atomic spectra in the particle phase are clearly detected that consistently agree with NIST database. For the first time, the in situ verification of the Na releases accompanying with coal devolatilization is fulfilled when the ambience temperature is high enough. The residence time, indicating Na release from particle to gas phases, is determined from the signal. By using a theoretical analysis, the Na release time approximately coincides with the characteristic pyrolysis time of lignite, further approving the observation above. The effects of ambience temperature, coal rank and oxygen concentration are further discussed. This work may initiate the possibility for exploring the formation of fine particulate during the coal combustion.