The disclosure provides a milling system and method under different lubrication conditions. The system uses a tool to mill the workpiece, a force measuring system to measure the milling force, a tool change system to replace the tools, a tool storage to store the tools. It can store the tools, provide the lubricating oil to the milling surface, select different tools according to different processing conditions, select the best angle differences of the unequal spiral angle tools according to different conditions comprising dry cutting, casting-type lubrication, minimal quantities of lubrication or minimal quantities of nanofluid lubrication, and/or choose the optimal tool according to different cutting parameters in order to obtain the minimum milling force.