The potential energy surface of HO2 is obtained using an algebraic method to fit ab initio data. The result shows that: the potential energy surface of HO2 has a small barrier (≤ 0.1 eV) on the incoming channel with ∠HOO≈ 120°, but the outgoing channel does not have an activation barrier. In order to test the accuracy of the potential energy surface, we calculate the force constants, dissociation energies, and the vibration energies. Comparing the results with those found by another method, we can see that the method we used here is good. This work offers people a way to calculate the vibration energies for transition state molecules.