Abstract: Pressure-activated sealants (PASs) are activated by a pressure differential only at leak points and therefore do not block normal wellbore flow paths, showing advantages in lost circulation management in mature oilfields. However, the sealing strength of reported PAS remains insufficient under complex downhole conditions, affecting oil well maintenance and long-term operational safety. Therefore, a leakage-point self-suspending PAS system based on ferric ion-dynamically crosslinked latex, namely F-PAS, was developed. Carboxylated nitrile butadiene rubber latex was used as the matrix, and an Fe³⁺ coordination crosslinking network was introduced to enable intelligent remediation of leakage points through pressure activation during downhole wellbore sealing operations, while maintaining excellent injectability and high pressure-bearing capacity. Under laboratory conditions, a systematic evaluation was conducted on the structural characteristics, dispersion stability, critical initiation pressure, and ultimate pressure-bearing capacity of F-PAS. The results indicate that F-PAS exhibits superior dispersion stability, with a critical initiation pressure of 234.514 Pa. Under simulated micro-fracture conditions in a cylindrical model with 500 μm diameter × 10 mm length, F-PAS achieves an ultimate plugging strength of 73.42 MPa. Mechanistic analysis reveals that Fe³⁺−carboxyl coordination forms a reversibly reinforced network, endowing the material with adaptive behavior and partial self-healing capability during the plugging process. This research provides an efficient and controllable novel chemical sealing solution for the intelligent remediation of wellbore integrity in mature oilfields, holding significant engineering application value for the safe and efficient development of oil and gas wells.