An imaging method comprising: generating a simulation model based on a physical structure of a detector module; for each of crystals comprised in the detector module, determining a reference energy weighting factor corresponding to each of a plurality of depth positions of the crystal based on the generated simulation model, wherein determining the reference energy weighting factor corresponding to the depth position of the crystal comprises: acquiring a maximum energy output by the crystal at the depth position; acquiring a total energy output by the detector module when the crystal outputs the maximum energy; and determining the reference energy weighting factor corresponding to the crystal at the depth position according to a ratio between the maximum energy and the total energy; determining associations between the plurality of depth positions of the crystal and the determined respective reference energy weighting factors for the crystal; receiving single event signals produced in the detector module and associated with a single event; determining a hit crystal in the detector module corresponding to a maximum single event signal of the single event signals; determining an actual energy weighting factor of the hit crystal, wherein determining the actual energy weighting factor comprises: obtaining a maximum energy output by the hit crystal; obtaining an actual total energy output by the detector module when the hit crystal outputs the maximum energy; and determining the actual energy weighting factor of the hit crystal according to the maximum energy output by the hit crystal and the actual total energy output by the detector module; determining an actual depth position corresponding to the actual energy weighting factor of the hit crystal according to the associations between the depth positions of the hit crystal and the respective reference energy weighting factors for the hit crystal, as an acting position in the detector module for the single event; determining a response line of a coincidence event according to respective acting positions in the detector module for two single events constituting the coincidence event, the two single events including the single event; and reconstructing an image according to the response line. generating a simulation model based on a physical structure of a detector module; for each of crystals comprised in the detector module, determining a reference energy weighting factor corresponding to each of a plurality of depth positions of the crystal based on the generated simulation model, wherein determining the reference energy weighting factor corresponding to the depth position of the crystal comprises: acquiring a maximum energy output by the crystal at the depth position; acquiring a total energy output by the detector module when the crystal outputs the maximum energy; and determining the reference energy weighting factor corresponding to the crystal at the depth position according to a ratio between the maximum energy and the total energy; determining associations between the plurality of depth positions of the crystal and the determined respective reference energy weighting factors for the crystal; determining a reference energy weighting factor corresponding to each of a plurality of depth positions of the crystal based on the generated simulation model, wherein determining the reference energy weighting factor corresponding to the depth position of the crystal comprises: acquiring a maximum energy output by the crystal at the depth position; acquiring a total energy output by the detector module when the crystal outputs the maximum energy; and determining the reference energy weighting factor corresponding to the crystal at the depth position according to a ratio between the maximum energy and the total energy; determining associations between the plurality of depth positions of the crystal and the determined respective reference energy weighting factors for the crystal; receiving single event signals produced in the detector module and associated with a single event; determining a hit crystal in the detector module corresponding to a maximum single event signal of the single event signals; determining an actual energy weighting factor of the hit crystal, wherein determining the actual energy weighting factor comprises: obtaining a maximum energy output by the hit crystal; obtaining an actual total energy output by the detector module when the hit crystal outputs the maximum energy; and determining the actual energy weighting factor of the hit crystal according to the maximum energy output by the hit crystal and the actual total energy output by the detector module; determining an actual depth position corresponding to the actual energy weighting factor of the hit crystal according to the associations between the depth positions of the hit crystal and the respective reference energy weighting factors for the hit crystal, as an acting position in the detector module for the single event; determining a response line of a coincidence event according to respective acting positions in the detector module for two single events constituting the coincidence event, the two single events including the single event; and reconstructing an image according to the response line.