To meet the required functional and nonfunctional requirements of different enterprise applications it is important to model the possible design so that a feasible alternative can be defined. We observed SaaS developed application by multi-tenancy to provide flexible customization and introduced many issues in software scalability and dynamic testing. Multi-tenancy demand to customizing the single instance according variability wishes among many customers. For that we proposed variable service process to customization multi-tenancy in runtime. It will be realize all benefits of variability concept for SaaS application.