The structural, electronic, optical, and elastic properties of Silicon doped Strontium Selenide binary and ternary semiconductor alloys with the general form of Sr((1-x))SixSe, 0 <= x <= 1 in B1 and B3 phases have been figured adopting augmented plane wave plus local orbital methods within density functional theory, Structural properties summarize the crystal structure, relevant atomic positions, lattice constant, bulk modulus minimum energy E0 and minimum volume V-0. Elastic constants conform to the structure stability of the B1 and B3 phases. Band gap is found to shift from indirect to direct and in some materials with initial direct band gap, the gap width increased which increased the range of applicability of these binary and ternary semiconductor compounds. Whereas optical properties which include the study of zero frequency limit of static dielectric constant e0(co) with its real and imaginary parts, static refractive index n(0), optical reflectivity (R), optical absorption coefficient (alpha), and loss function (L) studied comprehensively to get real electrical and optical properties of these materials and give semiconductor market best alternative candidate which shows its effectiveness in the visible, ultraviolet and infrared region of the electromagnetic spectrum. The obtained results were compared together and with the available experimental along with theoretical work on these binary and ternary Silicon doped Alkaline earth chalcogenides.