Abstract: Thin bed and multi-wave joint inversion are two major research focuses in fossil energy exploration.In the paper,two types of thin-bed coal models including strong impedance difference (model I) and weak impedance difference (model II) have been built.These researches were based on reflection and transmission coefficient of thin layer in frequency domain.Then elastic parameters of the models could be respectively predicted by using P-wave,S-wave inversion and PP&PS joint inversion.Model error analysis and inversion result were used to evaluate the effect of inversion methods,have theoretically confirmed that joint inversion of PP&PS is better for thin bed model than single inversion of P-wave or S-wave.