The photophysics of polystyrene had been the focus of much research.One common feature of their studies is that the absorbance and emission spectrum in solid films and solutions. A principle goal of this work has been understand the behavior of polystyrene under the effect of different solvents, concentrations as well as effect of quencher on the optical properties. The polystyrene emission is efficiently quenched in the presence of relatively concentration of the diethyl phthalate quencher at room temperature. Polystyrene solutions and solid films had maximum absorption intensity at 262 nm. The addition of diethyl phthalate did not change the absorption peak position. Polystyrene in (chloroform, cyclohexane and dichloromethane) shows fluorescence monomer emission at 296 nm, while the excimer emission recorded for polystyrene in (chloroform, cyclohexane, dichloromethane and tetrahydrofuran) at 307 nm 325 nm, 327 nm and 330 nm respectively. The emission spectrum of polystyrene films shows a strong red shift as compared with the emission spectrum in solution state; this is because of the extended conjugation of the polymer. The effect of concentration and quencher on the energy gap of polystyrene had been studied, where increasing of the concentration of polystyrene or the quencher leads to reducing of the energy gap.Solvents haveeffect on the fluorescence quantum yield magnitude, where highest value of it had been recorded for polystyrene in cyclohexane (55%).