Purpose: During the past several years there has been used of SPECT for optimizing the diagnostic capabilities by single photon imaging. SPECT produces computer‐reconstructed gamma‐ray images by up‐taken radiotracer. The existing clinical SPECT have two scintillation NaI(Tl) detectors, positioned at 90° to 180°. The purpose of this study is to test the feasibility of SPECT system consisted of fabricated CsI(Tl)‐PIN photodiode detectors with circular geometry like PET and CT geometry for multi‐modality applications. Methods: The sensors are fabricated with CsI(Tl) scintillator which is matched with PIN photodiode. And The single CsI(Tl)‐PIN photodiode detector are housed with a preamplifier and a shaping amplifier. Each detector's energy spectrum was measured by standard NIM module system. The detectors of SPECT system were positioned at angular interval of 18° in circular geometry. The imaging data of 137 Cs source was obtained by an SCA(single channel analyzer) and a counter system. Results: The average energy resolution of detectors was 11.16 % at 662 keV from 137Cs gamma‐ray source. The feasibility test of SPECT system for image was performed at five positions included center position of system. Conclusions: In this study, CsI(Tl)‐PIN photodiode detectors' energy spectrum were measured. The feasibility test was performed for SPECT system application. The detectors show appropriate energy resolution for SPECT application. By measuring of gamma‐rays at separated positions, we could reconstructed gamma‐ray images according to various source locations.