The slurry polymerization of styrene with indenyltitaniumtrichloride (IndTiCl3) in combination with methylaluminoxane (MAO) was investigated to study the effect of Al/Ti mole ratio, polymerization temperature, and catalyst concentration. From the experimental results, it was found that the catalytic activity was the highest at Al/Ti mole ratio of 4,000 polymerization temperature of 50°c, and IndTiCl3 catalyst concentration of 2.65x1(T4 mol/l, and Ti3+ is the active species for styrene polymerization. In addition, it was studied in the styrene polymerization by using trimethyaluminum (TMA) to examine the effect of polymerization time, polymerization temperature, and TMA concentration. At the concentration of TMA more than 0.1391 mol/l, polystyrene can be produced. The catalytic activity decreased with the increment of the polymerization temperature. Soxhlet extractor and FT-IR technique were used to measure the properties of polystyrene product. Syndiotacticity of obtained polystyrene with using lndTiCl3 catalyst is higher than that with using TMA.