Poststack seismic inversion can be applied to inversion of P and S waves, but not to seismic converted wave. The shear reflection coefficient can be obtained from converted wave using the relationship between reflection coefficients of the converted wave and the shear wave, which is a question of how to change poststack impedance inversion of converted wave into shear wave impedance inversion. Based on the inversion principle of well logging data, the initial shear wave impedance model was established using shear wave reflection coefficient and converted wave interpreted horizon. Optimizing inversion parameters helped the poststack impedance inversion of the converted wave. The inversion results lay the foundations of further study on lithology and parameters' comparison. Compared with S wave exploration, converted wave exploration is easy to operate and is low in production cost. Therefore, S wave impedance inversion of converted wave will be an economical method, but the precision of inversion result would be affected due to the approximate formula taken in calculation of shear reflection coefficient.