A tool-life prediction method, applicable to a machine tool having a machining end, includes steps of capturing a plurality of measurement data from a tool of the machining end, transforming each of the plurality of measurement data into a corresponding complex process capability index (Cpk), utilizing an artificial neural network being trained to generate a tool-life prediction scale with respect to the Cpk, and then based on the tool-life prediction scale to determine a remaining tool life of the tool. In addition, a tool life prediction system is also provided.