Fire sprinkler is a safety system that is active when fire is detected. It consists of a bulb that holds the water flow and made of glass with liquid inside. The increase of temperature in its environment would expand the volume of the liquid and break the glass which leads to water spray to extinguish the fire. This study aims to model and simulate the fire sprinkler bulb and optimize several parameters related to its activation including the thickness of the bulb, type of liquid and the ratio of air and liquid inside the bulb. The modeling and simulation was performed in COMSOL Multiphysics with variation of wall thickness and liquid inside the bulb. The result showed that the best parameter was the liquid of glycerol, a height of 17.5 mm and a glass thickness of 0.1 mm, this resulted in the air to liquid ratio of 0.0042428 and breaking time of 7.2400s. This result was the fastest breaking time towards several simulations. For future study, several parameters need to be considered in the simulation to minimize the gap between the simulation and the actual condition, such as room condition, and water pressure.