Samples with the composition Ge_2.5Sb_2.5Si_xTe_95-x (x = 10, 20, 30, 40) in atomic percentages were prepared by the melt quenching technique. The effect of replacing Te by Si atom on the physical properties such as, average coordination number, average heat of atomization, average single bond energy, glass transition temperature, optical energy gap, refractive index, molar refraction, electronic polarizability, and optical dielectric constant was studied. It was found that all the above parameters increase with increase in the Si content for all the studied glasses. The interpretation of results in terms of the average coordination number, and the average single bond energy is given.