Understanding the evaporation and decomposition process of bischofite precursor droplets in a pyrolysis furnace is the prerequisite for designing an efficient spray bischofite treatment facility. However, current research lacks guidance on this behavior. Here, it provided a new theoretical basis for understanding evaporation characteristics and decomposition behavior by introducing the Abramzon-Sirignano and kinetics models. In addition, the effects of ambient temperature and relative humidity on the evaporation characteristics of different precursors were analyzed. Meanwhile, the decomposition products and yield changes were studied in detail under different temperatures and times. The results show that the mass transfer coefficient and latent heat of vaporization have the most significant influence on droplet evaporation. To high recovery rate, the reaction temperature must be above 1125 °C. The current work can guide obtaining high magnesium oxide yield from waste bischofite in pyrolysis.