The nuclear spectroscopy systems are able to detect X and Gamma spectrums (distribution of the intensity of photons emitted from the source as a function of energy). In these systems, the gamma ray produced from the radioactive source emits a visible photon after colliding specific crystals such as sodium iodide and is detected; thus, such systems are among the main equipment in nuclear physics research labs, accelerators, and reactors, using neutron activation analysis methods and exploring radioactive materials in mines. The goal in performing this project at Nuclear Science and Technology Research Institute is based on design and construction of a nuclear spectrometry system with scintillation detectors. In this system, an electronic part consisting of a pre-amplifier, amplifier, pulse shaper, multi-channel analyzer and control systems register and process the scintillations and detect the energy and source flux consequently. The emitted wavelength for sodium iodide scintillating crystal is in green region. Due to the very low intensity of scintillations produced, a photon multiplier tube is used for the detection. The energy interval of the constructed system covers from 100 Kilo electron volt to 1.2 Mega electron volt. The resolution (separability) of the device is 1096 channels.