A multi-axis automatic tool-changing system for an automatic machining center which is disposed with a plurality of machining principal axes and a tool magazine. The tool magazine is disposed with a plurality of tool-changing positions located correspondingly to the machining principal axes. Between each machining principal axis and each tool-changing positions is disposed a tool-changing arm. Each tool-changing arm utilizes the first end and the second end tool-taking grooves to grasp and exchange the tools of the machining principal axes and the tool-changing positions.