This study scrutinizes the mechanism of femtosecond laser precision micromachining applied to face gear material 18Cr2Ni4WA. A comprehensive hydrodynamic model is proposed to elucidate the solid-liquid and gas-liquid phase transitions, taking into account factors including surface tension, Marangoni effect, buoyancy, gravity, and vapour recoil pressure. The investigation assesses the effects of varying pulse numbers, energy densities, and repetition frequencies of femtosecond laser on ablation crater depth and border morphology through model simulation and experimental trials. Findings indicate that a rise in laser pulse number and energy density enhances crater depth with divergent degrees of ablation crater edge elevation. An increase in laser repetition frequency escalates ablation line groove depth; optimal ablation morphology is identified at a repetition frequency of 300 kHz, while a poorer form is observed at 500 kHz due to increased melt accumulations within the ablation line groove. These insights offer the groundwork for advancing surface topography quality during femtosecond laser micromachining of face gear materials.