Abstract: The neutron emission time diagnostic was researched, and a bang time detector was made with ultra fast scintillator and microchannel-plate photomutiplier tube. The neutron emission time diagnostic was implemented in the implosion experiments at certain large-scale laser facility prototype, and the time interval between the beginning of the laser pulse and bang time was acquired. The experiment showed that DD and DT neutron can both be detetcted by the detector, and this detector can work in implosion experiments in which neutron yield is greater than 107, its timing precision is less than 20 ps. We found that the neutron emission time is relative to the thickness of CH layers clothed outside the targets in several shots.