Abstract: By analyzing the rolling cut machine, the paper cut unit of a printing machine and the profiled bar cutting equipment, this paper sums up two types of model and control arithmetic for fixed length cutting system. The rolling cut machine and paper cut unit are circle motion fixed length cutting systems. The profiled bar cutting equipment is a linear fixed length cutting system. Based on the equipment working principle, a model is established and a position control arithmetic is proposed. Compared with the traditional method which is often a velocity following system, the new control arithmetic has some characteristics of high precision, high speed, strong resistance of disturbing, and easy maintenance. A control flow chart for both of the fixed length cutting systems that can be used directly by numeral servo driver is obtained. The control method has been improved.