A laser based straightness measurement system for tube type works is designed in this paper. The technologies about centering, diameter acquiring and straightness computing are also developed. The self-centering sub-system uses a double cone coaxial centering method to achieve high-precision centering. Center coordinates are obtained by PSD and collimated laser. A rotation scanning sub-system is used to obtain radius and angle measurements which are used to rectify the centering error by applying least squares circle fitting algorithm. The straightness of the tube type work to be measured is finally calculated by using the above data obtained. Experimental results show that the system centering accuracy is up to 20μm, radial measurement accuracy up to 5μm, measurement repeatability up to 7μm, and straightness measurement accuracy less than 40μm.