Cement acoustic impedance calculation method and device

The invention discloses a cement acoustic impedance calculation method and device. The method comprises the following steps: acquiring a cement acoustic impedance calculation relation according to a previously established simulation model; acquiring an ultrasonic pulse reflection echo signal of the preset measuring point in the depth interval; acquiring calculating parameters of the cement acoustic impedance calculation relation according to the ultrasonic pulse reflection echo signal, wherein the calculating parameters comprise measured signal resonance wave normalized amplitude, ultrasonic pulse reflection echo signal frequency/casing thickness curve coefficient and free casing resonance wave normalized amplitude; and substituting the calculating parameters into the cement acoustic impedance calculation relation, and calculating the cement acoustic impedance of the current measuring point. The method according to the scheme can calculate the cement acoustic impedance under the condition of not needing free casing calibration, and enhances the computational accuracy.