Abstract: This paper introduces the faultprevention design and implementation of DFCCS（Dist- ributed Functional Control Computer System）.According to the fault classifications,the redundant kinds,the faultprevention level and the faultprevention technology,We create the realiable model of the DFCCS system.Then the evaluation of the faultprevention system is presented.The redundant methods and principles of faultprevention are introduced especially The evaluation model of the faultpreven- tion is proposed.This makes it easy for us to improve the performances of the faultprevention design.