The invention relates to the technical field of laser, in particular to a measuring device and a measuring method for piezoelectric ringing effect of an electro-optic crystal. The measuring device for piezoelectric ringing effect of the electro-optic crystal comprises a photoelectric detector A and a photoelectric detector B, and a film polaroid D, a half wave plate, a Faraday optical rotator, a film polaroid B, a quarter wave plate, a testing device and a total reflection mirror are arranged on a central line of an incident light path sequentially. The testing device is driven by a high-voltage drive power supply. The photoelectric detector A is used for detecting reflected light on the film polaroid D. The photoelectric detector B is used for detecting reflected light on the film polaroid B. Required voltage provided by the high-voltage drive power supply is reduced by half when the measuring device measures ringing effect of the electro-optic crystal, and measurement of piezoelectric ringing effect of high-voltage crystals such as BBO (barium metaborate) and a KD*P (potassium dihydrogen phosphate) crystal can be achieved.