$MoS_2$-based Ti composite coatings were deposited on the SCM420 alloy and gears using an RF magnetron sputtering (RFMS) system. While $MoS_2$ coating had been coated on the silicon substrate. The coatings structures were compared to each other to find the effect of Ti. The composite coatings have been tested in a ball-on-disk tribometer to investigate tribological behavior at various conditions. The scratch test was conducted to characterize adhesion force between composite coatings and substrates. The structure of the coatings has been extensively studied by a variety of techniques, including optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), etc. The composite coatings were also applied to the gears of a reduction gearbox. The efficiency of uncoated and $MoS_2$-based Ti coated gear was measured and compared at various input rotating speed under absorption oil film condition. It was found that the efficiency of gear had significantly improved after $MoS_2$-based Ti composite coatings deposition.