Abstract: Because description logic serves as the theoretical counterpart of the semantic Web and provide reasoning supports for it, the description logic reasoners are the basic supporting bodies for the semantic Web coming into use. Based on the fuzzy description logic F-ALC(G), the authors design and implement a description logic reasoner, named FRESG1.0, which can support the representation and reasoning of fuzzy customized data types and fuzzy customized data type predicates. Briefly introduced in this paper, are the reasoning services provided by FRESG1.0 and the program language of it. Also described are the overall architecture of FRESG1.0 and the design and implementation of its main components, where more attention is given to the features of the reasoner as well as the algorithms and technologies adopted in the process of implementations. From the testing cases, it can be seen that FRESG1.0 has more powerful reasoning capabilities in the representation and reasoning of the fuzzy customized data type information than other fuzzy description logic reasoners. FRESG1.0, which is open source under a very liberal license, is a complete and capable fuzzy description logic reasoner with acceptable good performance, extensive middleware, and a number of unique features, so it lays a foundation for its future investigations and extensions.