Multi-core systems have been a popular design for high-performance embedded systems. Scratch Pad Memory (SPM), a software-controlled on-chip memory, has been widely adopted in many embedded systems due to its small area and low energy consumption. Existing data allocation algorithms either cannot achieve optimal results or take exponential time to complete. In this paper, we propose one polynomial-time algorithms to solve the data allocation problem on multi-core system with exclusive data copy. According to the experimental results, the proposed optimal data allocation method alone reduces time cost of memory accesses by 16.45\% on average compared with greedy algorithm. The proposed data allocation algorithm also can reduce the energy cost significantly.