Perovskite/silicon heterojunction tandem solar cells have developed rapidly in recent years, and their efficiency is enhanced from 13.7% to 29.1%. As is well known, the optical loss has a great influence on the efficiency. Due to the complex fabrication process of tandem solar cells, it is important to obtain high-performance tandems through optical simulation. In this paper, optical simulation methods are mainly summarized from two aspects: commercial software and self-built model. Then, the progress of optical simulation is analyzed in terms of reflection loss and parasitic absorption. Finally, what should be paid more attention to in the optical simulation of tandem solar cells is pointed out. The efficiency limit of perovskite/silicon heterojunction tandem solar cells can reach up to 40%, but there remains much room for improvement. The research on optical simulation will lay the foundation of developing the tandem solar cells.