Abstract: An auto tools change with space allowance for tool rejection of spindle includes an arm seat, an arm shaft, a tools change arm, a flat cam, and a driving arm, while the flat cam has a driving groove for driving the driving arm to swing and thus facilitates the tool clamping and tool unclamping. Therein, the driving arm has a tool clamping section having an allowance groove, a first transition section, a tool unclamping section, and a second transition section. Therefore, a larger width of the allowance groove is provided on the driving groove, thereby offering a sliding space for the tools change arm. Thus, a space allowance is produced during tool pushing process, thereby not only preventing the main shaft and the tool from being damaged, but also preventing the tools change arm from deformation.