Single crystal diamond (SCD) exhibits excellent optoelectronic properties and is an ideal material for electronic and optical devices. However, its high hardness and chemical inertness result in low processing efficiency. In order to develop an efficient processing method, the influence and mechanism of reaction forms and reaction rates on the tribological behavior of SCD surfaces were investigated through ball-on-disk friction and wear experiments. The synergistic effect of the UV photocatalytic-Fenton composite reaction to produce hydroxyl radicals (•OH) was confirmed through the results. The •OH produced during the chemical reaction could react with SCD and Si3N4 surface materials, increasing the cutting depth of abrasive. The friction state is transformed from "three-body" rolling friction to "two-body" sliding friction, resulting in an obvious chemical-mechanical synergistic removal effect, which improves the processing efficiency and surface quality of SCD materials. Under the combined reaction, the material removal rate (MRRSCD) and the grinding ratio (G) reach their highest values, reaching 582.2 μm3/min and 0.925 μm/min, respectively, which are approximately 7 times and 6.5 times higher than those without the reaction. This study proposes a novel method for the high-efficiency ultra-precision machining of SCD.