To meet the need of large removal allowance and high efficiency of machining SiCp/Al surface, taking narrow slot mill-grinding as a typical example, the influence of machining parameters and mill-grinding tool on SiCp/Al machining force was experimentally investigated. The results show that the mill-grinding force is increased with the increasing speed and feedrate, and the feedrate is a significant impact on the force. In machining narrow-slot, the mill-grinding force can be reduced obviously by using the grinding tool with helix flutes. However, the mill-grinding force is fluctuant, and the fluctuant amplitude is reduced by reducing helix. Under the given conditions, the recommended helix of the wheel with flutes in mill-grinding narrow-slot is 50° which can perform a relative stabile machining process.