We present a systematical study on the roles of interactions among electron correlation, electron-phonon coupling, and spin-orbit coupling in the isovalent Pd-substituted superconductor SrPt3P. By using the solid state reaction method, the Pd element with the 4d orbital was successfully substituted in the strong spin-orbit coupling superconductors Sr(Pt1-xPdx)(3)P. As increasing the isovalent Pd concentrations without introducing any extra electron/hole carriers, the superconducting transition temperature T-c decreases monotonously. In addition, combining the data of resistivity and specific heat, as well as electronic band structure calculations, we found that the electron correlation is enhanced while the electron-phonon coupling and the spin-orbit coupling are suppressed by Pd substitution. Our results may provide significant insights in the natures of the interplay among the electron correlation, electron-phonon coupling, and spin-orbit coupling in superconductivity, and may also pave a route for understanding the mechanism of superconductivity in heavily 5d-based superconductors.