Titania nanopowders were synthesized by using microwave plasma synthesis technique. The effect of various processing parameters was systematically studied in this work. Manipulating the synthesis parameters such as the flow rate of plasma gas and feeding rate of precursor material (TiCl₄) can be used to control the average particle size and crystal phase of TiO₂ nanopowders. This method is clean, direct, convenient and simple without the need of further purification of the product powders. The photocatalytic activities of TiO2 nanopowders for the degradation of methylene blue have also been determined in liquid/solid system.