Abstract: Category theory is a mathematical theory to process abstractly mathematical structures and the relations among them．Bigraph which uses category theory as mathematical base,is a design,simulation and analysis platform for ubiquitous information systems．There,however,is a lack of specification,and are some errors in the definitions for bigraphical categories．The definition of bigraph basic signature was improved,and the juxtaposition operation of place graphs was corrected,and the relations among precategory,category,s-category and symmetric partial monoidal categorywere revealed in conjunction with giving an algorithm to construct bigraphical categories in this paper．Therefore,bigraph theories and its applications will be further investigated.

Key words: Bigraph,Category,Ubiquitous information system