  We have constructed all the three-family ${\cal N} = 1$ supersymmetric
Pati-Salam models from intersecting D6-branes, and obtained 33 independent
models in total. But how to realize the string-scale gauge coupling relations
in these models is a big challenge. We first discuss how to decouple the exotic
particles in these models. In addition, we consider the adjoint chiral
mulitplets for $SU(4)_C$ and $SU(2)_L$ gauge symmetries, the Standard Model
(SM) vector-like particles from D6-brane intersections, as well as the
vector-like particles from the ${\cal N}=2$ subsector. We show that the gauge
coupling relations at string scale can be achieved via two-loop renormalization
group equation running for all these supersymmetric Pati-Salam models.
Therefore, we propose a concrete way to obtain the string-scale gauge coupling
realtions for the generic intersecting D-brane models.
