[en] Organic single crystal stilbene has the best spectrometry characteristics and light yield in comparison with plastics and liquids and has been widely used as neutron detectors or monitors due to their fast timing response and good pulse shape discrimination (PSD) properties in neutron/gamma mixed fields such as a particle accelerator, a generation IV nuclear reactor, a nuclear fusion reactor, and so on. However, single stilbene crystals are so difficult to obtain in large size that greater than 60-80 mm in diameter, and are also vulnerable to damage from thermal and mechanical shocks that its extensive use are limited. Recently, polycrystal composite stilbene based on grains of stilbene crystals have been developed in several Research Institute and it is manufactured in large size for neutron detection. We have investigated its characteristics, especially capability of neutron /gamma discrimination