Abstract: The NaI(Tl) crystal is a common material used in radiation detectors. Due to its interaction with radiation, it produces weak light signals, which need to be converted into electrical signals for processing by subsequent circuits using photomultiplier tubes (PMTs). Silicon photomultiplier (SiPM), as a novel type of light-to-electrical conversion device, offers advantages over traditional PMTs, including lower noise, smaller size, lower power consumption, and magnetic field resistance. Based on SiPM, this study designed and developed a 1-inch NaI(Tl) detector. The detector boasts small size and low background noise. Through optimization of the detector’s physical structure and signal processing circuits, efficient detection of gamma rays was achieved. Additionally, the detector’s impact on the energy spectrum of a ¹³⁷Cs source was tested, revealing an energy resolution of 8.72% for 0.662 MeV gamma rays.