Electron beam welding (EBW) has an important role in industrial applications such as semi-conductor and LCD manufactures because of its high performance and accuracy. Since the operation is done in a vacuum room, it is very difficult to test the weldability as well as the correct welding area of the specimen. In this study, a measurement system of the EBW was developed based on the 3-axis LVDT controlled table. In addition, the algorithm to tracking the welding line has been developed. The weldability of the aluminum specimen was tested by a newly developed measurement system with ultrasonic C-scan inspection.