Abstract: With concise analysis methods, the mathematical model of the flying shear kinematics and its operating program in the computer have been developed, which is specially used for analysing the synchronous cutting characteristics of crank rotating flying shear with the radial equal speed mechanism both in its adjusting or running station on line and in the design of a new shear. The exactiude of the system has been indicated by comparing the calculated results with the situations of the shear's cutting operation.