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 $M_\perp \times_f M_T$. 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.