Energy production has become a major issue in the modern era of meeting energy demands. In this regard, we examined the mechanical, optical, electronic, structural, and thermodynamic characteristics of RbX2Ta3O10 (X = Ca and Mg) perovskite compounds by using the CASTEP code's based GGA-PBE approach. RbX2Ta3O10 (X = Ca and Mg) has a tetragonal-based structure with the space group p4/mmm (123) and the structure is stable according to formation energy - 7.579 eV and - 8.167 eV. According to findings, RbCa2Ta3O10 and RbMg2Ta3O10 material's electronic characteristics suggest that they have semiconductor behavior with indirect bandgap of 1.56 eV and 1.42 eV, respectively. To understand the relationship between light and its interaction with matter, the optical characteristics of substances were calculated and addressed in terms of the energy of photons. Mechanical properties analysis revealed that RbMg2Ta3O10 is a material with ductility (B/G = 2.04), while RbCa2Ta3O10 is brittle (B/G = 0.58). Elastic constant values are used to compute the following thermodynamic properties of RbCa2Ta3O10 and RbMg2Ta3O10: density (5.966, 5.854) g/cm(3), average sound velocity (3827.679, 3005.348) m/s, minimum thermal conductivity (1.091, 0.952) W/mK, melting temperature (842.370, 1147.290) K, and Debye temperature (440.438, 233.496) K. Our examination expected that these materials can be used in visible light photocatalytic processes devices to split water.