Rydberg atoms have large polarizabilities and transition dipole moments. They are extremely sensitive to external electric fields. Combining with the quantum interference effect, terahertz fields can be measured with high sensitivity. In this paper, we use a weak DC external electric field to tune the Rydberg state level to Förster resonance, thereby tuning the Rydberg pair interaction from the van der Waals interaction regime to the dipole-dipole interaction regime. This process creates an enhanced blockade effect and then enlarges the corresponding blockade region. The results show that the dipole-dipole interaction-induced blockade region can be 2-3 times larger than that of the van der Waals interaction. According to this characteristic, the external electric field can be used to enhance the blockade effect, which has reference significance for preparing high-quality unidirectional atoms and improving the accuracy of atomic detection in the terahertz-dressed Rydberg transition.