Abstract: To address the problem that the two-piece clamshell grab attachment of a material handling machine is prone to impact or gouge the material stacking platform during bulk material unloading and site-cleaning operations, this paper proposes an adaptive hydraulic system for site-cleaning working conditions based on an analysis of the motion trajectory during grab closing. The system uses angular displacement sensors to collect in real time the included angles among the boom, stick, and grab, enabling posture monitoring of the working device. Combined with a mechanical model, the pressure and flow requirements of the boom floating cylinder are calculated, thereby controlling the pump swash plate angle and the internal pressure of the floating cylinder. This allows the entire working device to float upward during the grab-closing process, ensuring that the motion trajectory of the grab teeth fully coincides with the cleaning working surface. Practical application demonstrates that the boom floating hydraulic system features high bucket filling efficiency, intelligent floating lifting capability, significant cost-effectiveness, and broad application prospects.