Simultaneous design of multiple products has become essential for manufacturing firms to expand design optimization basis. Various viewpoints on this issue have been provided from investigation of practices, but their outcomes still stay on descriptive stages. This paper discusses product variety design under modular architecture and module commonalization toward a computational methodology. It reviews the module based product variety with a mixture of views from customer’s needs, functions, manufacturing modules and hierarchical representation of systems. Based on the consequent framework, this paper also mathematically formulates the problem of product variety design as a 0-1 integer-programming problem in a systematically abstract form, and develops an optimization algorithm based on a simulated annealing technique. These discussion and optimization method are applied to a virtual design problem of television receiver circuits to show their validity and promise.