SM (Sulfur mustard) is an oily, hydrophobic, and lipophilic chemical agent that damages cells with intricate patterns. CEES (2-chloroethyl ethyl sulfide soluble) is a standard SM analog commonly employed in the toxicity mechanism study. To obtain ideal results in vitro, researchers should disperse CEES well in the medium, avoiding the presence of undissolved droplets. However, such a purpose is not easy to reach under the conventional solution preparation, and the information about droplet formation and function is little available. Here, we showed that phospholipid and triglyceride, two essential components of serum lipids, could prevent CEES from dissolving in water after vortex, which kept partial CEES as small droplets. By detecting CEES level, we proved that residual droplets slowed CEES hydrolysis and conversion. Under the microscope, CEES droplets were observed to degrade and diffuse with time to induce the necrosis and mitochondrial membrane potential decline from nearby cells. In conclusion, the damage pattern of CEES droplets is quite different from that of dissolved CEES, and a low level of phospholipid and triglyceride is beneficial for preventing droplets formation in preparing CEES solution.