A holographic data storage (HDS) has some advantages of high storage capacity, fast transmission, and short access time. However, there are two major concerns with the system which are two-dimensional (2D) inter-symbol interference (ISI) and inter-page interference (IPI). Thus, this paper proposes a 4-level 6/9 modulation code which mitigate inter-symbol interference (ISI). (inter-page interference, IPI)이 존재한다 [1][2][3] . 그리고