Abstract: Rapid 3D induced polarization (IP) inversions algorithm are developed using conjugate gradient (CG) relaxation techniques. At the first stage,the 3D resistivity model is recovered by inverting dc potential data using CG method, it bypasses the computation of the derivative matrix, therefore, the resistivity inversion is computed much quickly. Then, the 3D resistivity model is accepted as the distribution of subsurface resistivity to obtain a chargeability that satisfies the IP data. The algorithm is tested using synthetic model and it shows promising results.