Motorcycle crankshaft is a special rigid rotor. It is composed of crankshaft, connecting rod and slider. It belongs to unbalanced rotor. Most of traditional methods of measuring unbalance value of crankshaft are not continuous, which need human intervention. So the measurement time is long and measurement accuracy is not high. To solve the above problem, a novel computer-based measurement is developed. The software of the measuring system is developed based on G-language, namely LabVIEW. The hardware system includes accelerate sensors, multi-function Data Acquisition (DAQ) card and industrial control computer. When the crankshaft rotates, its centrifugal forces are generated which result in the supporting structure (also called vibration table) vibrating. Data acquisition, signal processing and analysis can obtain unbalance value including amplitude and phrases. Computer-based measurement is used with software to set up automated test system that can make fast measurements without human intervention. The application of virtual instruments makes date analysis more accurate, and decreases the measuring time significantly; a complete measurement can be finished in 25s. The results show that this new measuring system has the advantages of easy-of-use, high precision, high efficiency and low costs.