Arsenic contamination in groundwater has been recognized as a serious issue for health and environment because arsenic is a hazardous and toxic element; therefore, developing new technology is significant to remove arsenic from groundwater. Technology of arsenic removal has been in place through research to mitigate this problem, including aeration approach, Haix absorbent, precipitation, absorption process, and membrane technology. This study aims to evaluate and investigate new method of removing arsenic by applying the combined process of coke-bed trickling filter and sedimentation. One tubewell water from Koh Thom district, Kandal province, in Cambodia was chosen for the study. The concentration of total arsenic (As-T), arsenite-arsenic (As(III)), arsenate-arsenic (As(V)), pH, Mn, and Fe were analyzed. The combined process of coke-bed trickling filter and sedimentation was conducted with four different Phases (A, B, C, D). Phase A represents the flow rate of 1.0 L/day of pumping influent groundwater sample with aeration, and without introduction of iron. Phase B represents the flow rate of 1.0 L/day of influent sample with aeration and introduction of 25 mg/l of iron added. Phase C and D represents the flow rate 1.5 L/day and 2 L/day; respectively, of influent sample with aeration and introduction of 25 mg/l of iron added. The concentration of As-T was removed in Phase A by 29%. Whereas the concentration of As-T showed high effectively removal from 80 to 86% in Phase B, C and D. Specifically, the total concentration of As decreased from 356.25 μg/L to 48.75 μg/L, 108.75 to 21.625 μg/L, and 472.5 to 75 μg/L for Phase B, C, and D; respectively. In conclusion, this combined process could be an effective technique to remove As from groundwater.