The invention provides a method for detecting the accuracy of a CT photon counting type detector, relating to the technical field of medical treatment equipment. The method comprises the following steps: building a CT scanning system by virtue of an x-ray bulb tube, a triangular prism-shaped double-material mold body and a common flat panel detector, and scanning so as to obtain a first group of data; removing the mold body, and carrying out empty scanning so as to obtain a second group of data; constructing a linear equation set based on an attenuation transmission principle according to the two groups of data, and solving to obtain a first x-ray dispersion energy spectrum; replacing the common flat panel detector with a to-be-detected photon counting type detector, removing the mold body, and carrying out empty scanning so as to obtain a second x-ray dispersion energy spectrum; and making comparison on the two dispersion energy spectra, wherein when the error is within a certain range, the accuracy of the photon counting type detector meets the requirements. According to the method, the triangular prism-shaped double-material mold body is arranged, and the energy spectrum measurement is carried out by virtue of two attenuation substances based on the attenuation transmission principle, so that the morbidity of a to-be-solved linear equation set is fundamentally and effectively improved; and the structure of the mold body is simple, the scanning number of times is few, the wasting of resources is effectively avoided, and the reliability is high.