Abstract：Based on testing data，a biparametric equation is presented to depict the rupture shape of prestressed cable. According to the ultimate equilibrium principle and Hoek-Brown criterion，the ultimate pullout force of prestressed cable is studied and a ultimate-value principle is suggested. A calculation example is given. The results show that the ultimate pullout force is related to the rupture shape of prestressed cable，rock type，unconfined compressive strength of rock，weathering degree，grouting material and grouting pressure，etc. At last，a series of formulas are given to determine the ultimate pullout force and lateral resistance of prestressed cable.
