<p>As an emerging green technology without the thermal effects and tool wear, Abrasive Water Jet (AWJ) machining offers distinct advantages over the traditional numerical control machining methods in tackling some hard-to-cut materials, such as high-hardness alloys and composite materials. The non-thermal nature of AWJ machining prevents surface burn, while the absence of direct tool contact eliminates tool wear and machine vibration caused by conventional cutting forces. In the AWJ machining, the side cutting uses only a portion of the jet beam for processing. Unlike the conventional AWJ machining that employs a jet at the end effector for through-cutting, the side cutting offers advantages such as more stable fluid erosion process and higher machining quality. However, research on the formation conditions, fluid characteristics, and influence of process parameters of side cutting remains unclear. This study proposes an innovative theoretical analysis method for AWJ side cutting, in which the interaction between the fluid core zone and the workpiece is investigated to elucidate the influence of fluid behavior on the jet side-cutting process. Combined with experimental studies, a systematic investigation is conducted into the influence of process parameters on side cutting depth and the formation conditions of side cutting, and the results show good agreement between experiments and theoretical analysis.</p>