The concept of parallel-computing based MPI and the implementation of parallel-computing cluster are introduced. The parallel way of image processing arithmetic is presented. Some methods of impoving parallel efficiency are put forward. A matching arithmetic based on intensity-based correlation and the FFT arithmetic are implemented and run on the parallel-computing cluster. The results are analyzed and compared. The expermental data show the relationship of computing efficiency and the quantities of communication. The feasibility scope of parallel computing in image processing is put forward.