Combinatorial methodology has been proven to be a powerful tool in exploring novel materials because of its effectiveness in accelerating fabrication efficiency and optimization for searching functional materials. In this study, the methodology was incorporated into a facile spin coating method for the first time to exploit TiO2-rGO nanorod nanocomposites for achieving synergistic photocatalysis. Graphene has been studied in various fields due to its unique electronic properties, including excellent charge carrier mobility, and extremely high surface area. If it is combined with a semiconductor photocatalyst, its features will make substantial electron-hole pair recombination reduction in the system, thus leading to a synergistic photocatalytic performance. In this study, graphene was incorporated into a density gradient of TiO2 nanorods fabricated using combinatorial methodology to study their coupling and obtain the optimal combination for the photocatalytic applications. A TiO2 seed layer gradient was formed on a Si substrate via spin-coating using a home-made tilt-angle stage. Subsequently, a hydrothermal reaction was performed to grow density gradient TiO2 nanorods. Graphene oxide (GO) was then uniformly deposited on it using spin-coating. The resulting sample was reduced under UV light irradiation to obtain the density gradient TiO2-rGO nanocomposites. Scanning electron microscopy (SEM) was applied to study the density variation of TiO2 nanorods; x-ray diffraction (XRD) and tran mission electron microscopy (TEM) were carried out to obtain the crystallinity and microstructures of the samples. The composition and the reduction ability of GO analyses were studied by x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, respectively. The optical properties were measured through UV-vis spectrophotometry (UV) and photoluminescence spectroscopy (PL). The density gradient TiO2-rGO nanocomposite was cut into four pieces along the gradient direction and their photocatalytic efficiencies were measured individually by photodegrading methylene blue (MB) solutions. The results suggested that TiO2 density was crucial to achieve superior photocatalysis, attributed to effective irradiation absorption. We demonstrated combinatorial methodology as an efficient approach to explore excellent photocatalyst from a wide range of TiO2 nanorod density space.