Assembly processes are very complex and hard to setup in one-time for large-scale products. Much assembly information is produced in various assembly processes and such information has not integrated or considered for next assembly processes. This leads to problems of deciding manufacturing tolerance of productions quality in the final assembly process. An object-oriented assembly information model and visualization for VAFM (Virtual Assembly Fat Model), is presented in the paper. The information modeling for assembly processes considers not only geometry data, but also non-geometry information, and those information produced by assembly process evolve, mature and derived during the whole assembly process. The paper presents modeling language based on XML and distributed storage based BSON for assembly object. The visualization of VAFM is also presented.