Activation of Nrf2 by directly inhibiting the Keap1-Nrf2 Protein-Protein Interaction (PPI) has gained research interest with regard to developing novel agents for treating inflammatory related diseases. In this study, computational methods were used to guide rational activity improvement of peptide Keap1-Nrf2 inhibitors and to explore Keap1 binding cavity. Terminal hydrophobic residues and Tyr residue replacements were introduced into the novel peptides. The experimental values of these peptides further confirmed the potential binding sites explored by the MD simulation. Finally, the most promising peptide 5 with the intracyclic conformation showed a Kd value of 2.8 nM binding to Keap1 and IC50 value of 9.4 nM in the Keap1-Nrf2 PPI fluorescence polarization assay. It proved that the active conformation locking strategy is quite useful in Keap1-Nf2 PPI inhibitor design. It also provided a useful probe to investigate the Keap1-Nrf2 PPI system.