The pulsed electro-acoustic (PEA) method has been developed to measure space charge phenomena in dielectric materials. This method is widely used for the space charge measurement not only on polymer, but also on other dielectric materials. It is considered that the difference of acoustic characteristics of each dielectric material can make measurement error in the 2-layer dielectric. This error used to be examined by the theoretical formula on transmission and reflection using acoustic impedance. However, it was difficult to analyze simultaneously both spatial and transient phenomena in generation and propagation of acoustic wave in the space charge measurement by this formula. So, we have proposed the numerical analysis model for generation and propagation of acoustic wave in order to discuss the error factors in space charge measurement. In this paper, the numerical analysis of experimental results in 2-layer dielectric has probed that the effects of the acoustic characteristics of electrode and 2-layer dielectric and the difference of dielectric constant of samples on the results of space charge measurement can be caused.