In order to make much detail monitor and more practical evaluation on structural safety and durability for long-span continuous rigid frame bridge, the condition for prestressing reservation in service stage turns out to be a necessary key index. By means of obtained stress value on prestressing tendons, discrimination on subordinated mode and recognition on nominal coefficients of prestress losses are implemented. Furthermore, unified evaluation on effective prestress of post-tensioned PC bridges are realized at anytime of the whole service life, which include different geometric patterns of prestressed reinforcement, different types of structure and different structural formation systems. Simultaneously, recognition on two types of nominal coefficients for prestress losses is realized and regularities of practical distribution can be simulated. The practical utility of a long-span continuous rigid frame bridge show that the general principle for effective prestress can be demonstrated. Therefore, key parameters for health monitoring on existing long-span continuous rigid frame bridge are provided and the results lay the foundation for further control.