Buffer overflow vulnerability is currently one of the major security problems for programming languages written in C/C ++. To address this issue, existing studies have proposed varied detection techniques to eliminate buffer overflow vulnerability. However, these approaches are still far from finding an ideal solution to completely reduce buffer overflow vulnerability. This paper presents a detection approach for buffer overflow vulnerability based on Data Control Flow Graph (DCFG). The proposed approach first uses the dangerous function identification method to determine the dangerous points and the type of dangerous functions. We then construct the constraint rules of the dangerous function at the dangerous point to establish the constraint system. Finally, the constraint system is solved to obtain the result of the vulnerability determination. To explore this approach, we performed an extensive experiment and compared empirically with existing vulnerability detection tools. The result shows that the proposed method has a good effect on buffer overflow vulnerability detection, and can effectively improve detection efficiency.