Optics is an experiment-oriented lesson that plays an important role in middle school physics. Simulation technology based on game engine has attracted many educators and teachers to explore its application in pedagogy because it is attractive, interactive and low-cost. This paper designs an optical experiment simulation based on the Unity3D game engine, which implements three optical experiments: mirror reflection, water refraction and Young's double-slit interference. Furthermore, this paper constructs an optical experiment simulation software library, which can be reused to other optical simulation experiment system.