The arithmetic unit allocation is one of the key algorithm in the high-level synthesis. Mainly for digital signal process application, a linear regular datapath model is adopted whose main idea is to minimize the global interconnection. With the initial arithmetic unit allocation constructed by minimal coloring algorithm，stochastic evolution is used to improve the allocation in an iterative way, minimizing the number of the data registers and the data exchanged between the process units. Experiment results with typical design example are also presented.