The present disclosure provides a detection collimation unit, a detection apparatus and a SPECT imaging system. The detection collimation unit includes: a scintillation crystal array configured to receive a gamma photon emitted by a radioactive source in a detected object; and a number of photoelectric devices configured to receive the gamma photon and converting the gamma photon into a digital signal. The scintillation crystal array includes a number of scintillation crystals. The number of scintillation crystals are arranged substantially in parallel and are spaced from each other. Each scintillation crystal has a side face configured to receive a ray emitted by the radioactive source and an end face. The number of photoelectric devices are coupled to the end faces of the number of scintillation crystals. The detection collimation unit of the present disclosure may be used to replace a heavy metal collimator required for a SPECT imaging. This may reduce a loss of the gamma photon, avoid an absorption of the gamma photon by a circuit board and a photoelectric device in the detection collimation unit, and significantly improve a spatial resolution and a detection efficiency of the SPECT imaging. At the same time, a difficulty in a processing a plurality of small parallel holes or pinholes in the heavy metal collimator may be avoided, and the processing may be simplified.