Amorphous carbon (a:C-H) coatings with high hardness and low friction coefficient are widely applied in die and mold industries. Zirconium-containing a:C-H (a-C:Zr) coatings with double interlayered Zr/ZrC were deposited by unbalanced magnetron sputtering system. A L18 orthogonal array experiment was designed to investigate the effect of process parameter on the friction coefficient of deposited films. Control factors, such as methane flow rate, bias voltage, sputtering frequency, zirconium target current and work distance were schematized for experiments. The experimental results show that zirconium target current exhibits about 45% percent contribution in analysis of variance, and the friction coefficient of a-C:Zr coatings range from 0.13 to 0.31. From effect plots, the optimum parameters are bias voltage at -70V, zirconium target current at 0.6 A, pulse frequency at 90 kHz, methane flow rate at 6 sccm and work distance at 15 cm. The friction coefficient performs as 0.106 in verification experiments. Meanwhile, one-by-one factorial experiments were also carried out and discussed in this study.