Indium tin oxide (ITO) films were synthesized on polymer (PES, polyethersulfone) at room temperature by pulsed DC magnetron sputtering. By the control of introducing hydrogen to argon atmosphere, the resistivity of ITO films was obtained at $5.27;{ imes};10^{-4};{Omega}{cdot}cm$ without substrate heating in comparison with $2.65;{ imes};10{-3};{Omega}{cdot}cm$ under hydrogen free condition. ITO film synthesized at Ar condition was changed from amorphous to crystalline. These result from the enhancement of electron temperature in $Ar;+;H_2$ plasma, which induces the increase of ionization of target materials and argon. The dominant increase of ions such as In II and O II and neutral Sn I was monitored by optical emission spectroscopy (OES). Thermal energy required for the crystalline film formation is compensated by kinetic energy transfer through ion bombardments to substrate.