Doping represents one of the most promising avenues for optimizing superconductors, such as reaching record-breaking critical temperatures of hydride superconductors. In this work, we perform an thorough and extensive search for substitutional dopants in LaH₁₀, looking for elements that enhance its electronic structure (especially the density of states at the Fermi level). In total, 70 elements were investigated as possible substitutions of La-sites at the doping ratio of 12.5% under high pressure. By using our systemetical and efficient screening protocal, we found Ca as the best candidate dopants, which shift the van Hove singularity and increase the electronic DOS at the Fermi level. With harmonic-level phonon calculations and performin first-principles calculation of T_c, Ca-doped LaH₁₀ shows T_c which is 15% higher than the one of LaH₁₀. It provides a promising route to reach the room-temperature superconductivity in pressurized hydrides by doping. Meanwhile, this process of screening based on structure relaxation and electronic structure calculation can be generalized to apply to other clathrate hydride systems to reach higher T_c by optimal doping.