In order to obtain the information about the species and content of the formation elements in the process of petroleum logging, a logging tool used for detecting formation elements based on the pulsed neutron source is developed.The neutron source, controlled by the instrument, sends neutrons to the formation in the form of pulses, by controlling the timing of the pulses, the tool can get the energy of gamma ray produced during different stages of neutron reaction, then detailed energy spectrum and time spectrum data can be obtained. The experiments show that the instrument performance meet the design index, the instrument can effectively get the energy spectrum data consist of 256 energy channels, corresponding to 0-10MeV γray energy, including the inelastic scattering spectrum ,the neutron capture spectrum and the background spectrum; in addition, a 256 channels time spectrum corresponding to a 100ms neutron emission period is achieved. The experimental wells, such as pure water well, sour well and carbon bearing well, are tested using the chemical neutron source, and the measured results were in good agreement with the known data.