In the era of modern computing based environment, the process of design is conceptualized, implemented and tested in a close loop integrating different modules of design, manufacturing and usages. In this regard, this paper presents a computing based design model for the design of a 'Pneumatic Driven Variable Buoyancy System (PDVBS)' for 'Autonomous Underwater Vehicles (AUVs)'. The presented design model is modular in architecture and integrates the design of PDVBS with design of AUV. The design approach is derived from the basic and advanced principles of mechanics and the approach is defined in the 'Computer Aided Design (CAD)' model in terms of different modules with implementation in Matlab∗™. Finally, we present a design example of a PDVBS for depth rating up to 4200 m with application focused on a large AUV of length 7 m to show the efficiency and applicability of our proposed design model. © 2016 IEEE.