A new high-performance laser scanning optical system for the Computed Radiography(CR) with a spatial resolution of 10 lp/mm was designed. In view of the performance difference of scanning methods, a scanning arm composed of a pentagonal prism and a scanning object lens was presented to replace the Fθ lens,and then a circular imaging plate was presented to implement the transport mechanism by bending film movement.As the scanning arm can collect synchronously luminescence as a receiving device,the system designed by this method has a simple structure and good performance. The effect of spot sizes on resolution was analyzed and the results show that the smaller the spot size is, the higher the system resolution will be. Many factors effecting on the spot sizes were analyzed in this system,and the dynamic performance of the scanning arm was simulated by using the finite element method in high speed rotating.Furthermore, the influence of an incident light out of the vertical incident flat of pentagonal prism and pentagonal prism displacement errors on the spot sizes were calculated, and the calculation reveals that the largest change of the diameter for the spot sizes is 0.07%,which proves that the system has good tolerance and practicability. Experiments were carried out to verity the performance of laser scanner,and the results indicate that the images obainted have good visual effects and can meet the requirements of industrial inspections.