In this paper, the author puts forward a kind of parallel recognition algorithm in implementation of parallelization compiler[3]. Application programs in scientific and technological fields have grown increasingly large and complex, thus, it is becoming more difficult to parallelize these programs by hand using message-passing libraries. To reduce this difficulty, we are researching the compilation technology for serial program automatic parallelization. The algorithm uses the conceptions of medium grain parallel[2] and data dependence to realize the target of the program automatic parallelization. At the first, the author defines the data dependence of blocks by variables that the blocks have accesses at the same time. For another, by this definition, the parallelization compiler can identify all of the parallelizable blocks in the serial program and can provide a certain possibility to implement the application programs automatic parallelization. The goal to speed up the program and to improve the execution ability of the program can be realized when the blocks parallel execute on multi-processors. At the last, in the end of the paper, the author analyzes the performance of the proposed algorithm, so the author puts forward two strategies of parallel optimization.