Abstract: Compactness and moisture content, closely related with soil wave velocity and resistivity, are the key parameters affecting stability of expansive soil slopes. It is significant to evaluating stability of expansive soil slopes through studying the acoustic-electrical response of key above mentioned parameters of expansive soil slopes. This paper reveals the acoustic-electrical response characteristics of expansive soil with different compactness and moisture contents through a series of laboratory tests. When retaining a certain water content, the wave velocity of soil increases with the increase of compactness, however when the water content is 40% and the compactness is ≥ 80%, the change of wave velocity tends to be stable; When the compactness is a certain value, and the water content is ≥ 35% or ≤ 25%, the wave velocity curves cross with each other, in this condition the water content and compactness cannot be evaluated simply by the wave velocity. When the compactness (water content) remains unchanged, the water content (compactness) is negatively correlated with the change of resistivity, that is, the larger the water content or compactness is, the smaller the resistivity value is; When the water content is greater than 45%, the resistivity value basically tends to be stable, at this time, the resistivity cannot effectively represent the water content and compactness. In view of the limitations of using a single test method to evaluate the moisture content and compactness of expansive soil, we suggest using wave velocity and resistivity comprehensively to analyze physical features of expansive soil, which can improve the identifying accuracy on water content and compactness of expansive soil.