An afterglow detection device for detecting afterglow of a scintillation detector, comprising: an X-ray tube for emitting an X-ray beam; and a first reading circuit for receiving a first detected signal from the scintillation detector to form and output a first measurement signal according to the first detected signal, the scintillation detector being connected to the first reading circuit and disposed on a beam-out side of the X-ray tube to receive radiation of the X-ray beam and outputting the first detected signal to the first reading circuit at the time of detection; characterized in that the afterglow detection device further comprises: a residual ray detector for receiving radiation of the X-ray beam from the X-ray tube and disposed on a beam-out side of the X-ray tube, wherein the output relative intensity of the residual ray detector at the moment of 10ms after disappearance of an excitation signal is lower than 0.05% of the output relative intensity in the presence of the excitation signal; a second reading circuit connected to the residual ray detector for receiving a second detected signal from the residual ray detector to form and output a second measurement signal according to the second detected signal, the residual ray detector receiving radiation of the X-ray beam and outputting a second detected signal to the second reading circuit; and a computing device in signal connection with the first reading circuit and the second reading circuit to receive the first measurement signal and the second measurement signal, the computing device being configured to compute and output the afterglow detection signal according to the first measurement signal and the second measurement signal after a power supply for the X-ray tube is turned off. an X-ray tube for emitting an X-ray beam; and a first reading circuit for receiving a first detected signal from the scintillation detector to form and output a first measurement signal according to the first detected signal, the scintillation detector being connected to the first reading circuit and disposed on a beam-out side of the X-ray tube to receive radiation of the X-ray beam and outputting the first detected signal to the first reading circuit at the time of detection; characterized in that the afterglow detection device further comprises: a residual ray detector for receiving radiation of the X-ray beam from the X-ray tube and disposed on a beam-out side of the X-ray tube, wherein the output relative intensity of the residual ray detector at the moment of 10ms after disappearance of an excitation signal is lower than 0.05% of the output relative intensity in the presence of the excitation signal; a second reading circuit connected to the residual ray detector for receiving a second detected signal from the residual ray detector to form and output a second measurement signal according to the second detected signal, the residual ray detector receiving radiation of the X-ray beam and outputting a second detected signal to the second reading circuit; and a computing device in signal connection with the first reading circuit and the second reading circuit to receive the first measurement signal and the second measurement signal, the computing device being configured to compute and output the afterglow detection signal according to the first measurement signal and the second measurement signal after a power supply for the X-ray tube is turned off. a residual ray detector for receiving radiation of the X-ray beam from the X-ray tube and disposed on a beam-out side of the X-ray tube, wherein the output relative intensity of the residual ray detector at the moment of 10ms after disappearance of an excitation signal is lower than 0.05% of the output relative intensity in the presence of the excitation signal; a second reading circuit connected to the residual ray detector for receiving a second detected signal from the residual ray detector to form and output a second measurement signal according to the second detected signal, the residual ray detector receiving radiation of the X-ray beam and outputting a second detected signal to the second reading circuit; and a computing device in signal connection with the first reading circuit and the second reading circuit to receive the first measurement signal and the second measurement signal, the computing device being configured to compute and output the afterglow detection signal according to the first measurement signal and the second measurement signal after a power supply for the X-ray tube is turned off.