Five-axis NC machining tools can improve the efficiency and accuracy obviously in today’s machining industries, but the machining errors and tool interference are likely to happen due to the complexity of tool motion. So the verification of the tool path is very important and necessary before machining the part. A new algorithm for 5-axis machining verification based on the swept volume has been presented in the paper. Based on the machine tool path and the cutter geometry, the cutter’s instantaneous swept profile is determined. By integrating the intermediate swept volume, the cutter’s swept envelope can be constructed and applied to NC verification. The algorithm has been implemented through Visual C++ and OpenGL language on Windows XP platform; a few examples are to verify the reliability of the proposed algorithms effectively. The experiment results indicate that the proposed method is superior to the traditional methods on the processing time and image quality. This proposed algorithm can be further applied to machining error analysis, collisions interference and NC path optimization, etc.