The design of complex systems is a challenging task, combining optimization and testing techniques. Design space exploration allows the designer to optimize the parameters of the system, but is usually very costly and induces many inherent difficulties that require specific computation techniques to be solved. Qualitative reasoning was first introduced to describe system structures and causality, and developed to study the behavior of the system and discretize its state space into qualitative states. It is now used in diagnosis and verification to reduce computation time and precision while still preserving major properties of the behavior. This article presents how we think that qualitative reasoning can be applied to design space exploration in addition to state space discretization, i.e. how it may help in the choice of parameters for a system, by reducing the computational cost of this exploration.