SCADA systems play key roles in monitor and control of the critical infrastructures, the vulnerabilities existed in them may destroy the controlled critical infrastructures. This paper proposes an analysis method of memory access vulnerability in SCADA protocol implementation. Firstly, the memory taintedness model of SCADA protocol implementation is formally defined. Based on this model, the detection algorithm of memory access vulnerability is proposed. Finally, the model and algorithm are validated through the experiment of vulnerability analysis.