An interference preventing method applied on a machining machine includes the following steps. Firstly, a control command is provided in response to an operation event. Next, protection information corresponding to a protection target component is provided. Then basic envelop of the protection target component is obtained. Then the basic envelop is segmented into a number of sub protection blocks according to a multi-hierarchical protection parameter and sub protection blocks not linked with the protection target component are removed, so as to determine a multi-hierarchical interference protection area. Next, whether an interference event of the multi-hierarchical interference protection area and other components occurs, so as to determine whether interference event of the protection target component occurs; if so, control signal is provided to control the processing operation of the machining machine.