Abstract: First, on the basis of the product device hazard level rating, this paper presents the new concepts and relevant properties of Fuzzy language field and Fuzzy language value structure, sets the language field of hazard level as a standard language field, and all the factor language fields affecting hazard level are discussed in this standa rd language field so the description of the states of fire-hazardous level etc. transits to that of hazard level. Next, it presents the Fuzzy synthesize integrated algorithm, and forms a inte-gration of Fuzzy set theory, Fuzzy synthesis evaluation, Fuzzy clustering analysis, Fuzzy logic, Fuzzy linguistics, Fuzzy statistics etc. Then, it develops a software system of comput-er-assisted safe evaluation. Last, this software system is verified effectively in the appliction of many chemical industy instances.