The aim of this paper is to study the warped product semi-invariant submanifolds in a normal paracontact metric space form. We obtain some characterization and new geometric obstructions for the warped product type M ⊥ × f M T . We establish a general inequality among the trace of the induced tensor, laplace operator, the squared norms of the second fundamental form and warping function . These inequalities are discussed and we obtain some new results.