Diamond-like Carbon films were deposited onto the glass substrate at 50℃ by dual-ion beam sputtering method. The function of the sputtering apparatus was briefly introduced. The influences of the bombarding ion energy, the bombarding ion beam current density and the ratio of hydrogen to argon gas in bombarding ion source on the infra-red (IR) transmittanoe behaviour of deposited specimens were investigated in 1.5-5.6μm wavelength range. It showed that for all specimens, their relative transmittanoe increase with the increase of wavelengths. For each group of experiment in which only one parameter as described above varied, with the increase of varying parameter, the relative transmittance versus wavelength curves all have a trend to increase first and then to drop. The corresponding critical varying parameters in the four group of experiments were determined comparison between the non-hydrogenated and the hydrogenated specimens showed that hydrogen in the bombarding ion source was not strictly for the deposition of DLC films, but adding a certain amount of hydrogen could reduce the sputtering of growing films and could improve the IR transmittance behaviour of the films. The observed results were discussed and explained in terms of structure changes.