Abstract: The method of characteristics (MOC) solves the neutron transport equation along each characteristics line. Theoretically, it is independent of the geometry shape of boundary and region. However, the geometry should be described, and ray tracing sould be carried out firstly. In most of the existing MOC codes, the geometry description and ray tracing still have more or less limitation. To wipe off these geometry limitations for using MOC in more complex fuel assembly calculation, a new MOC code AutoMOC based on the customization of AutoCAD was developed. The numerical results show that AutoMOC not only has high flexibility in geometry but also gives accurate solutions in comparison with state-of-the-art methodologies.