The invention discloses a measuring method and device for PET detector and crystal interactive depth. The method includes that along the length direction of a crystal, the cross sections at the positions on the crystal at every preset distance are subjected to technological processing to form netted cross sections, the two ends of the crystal in the length direction are coupled to PET detectors respectively, point radioactive sources are successively arranged at one side of the crystal in the length direction and are aligned with the netted cross sections to carry out the measurement of the PET detector and crystal interactive depth. Therefore, by processing the crystal in such a method, the uniform irradiation of the point radioactive sources on the crystal side surface is high, and the aim of high accuracy of the measured data related to the interactive depth is achieved.