Abstract: Research of two discrimination methods on neutron and gamma ray has been carried out using a plastic scintillator detector EJ276 with 2 inches in diameter and 2 inches in length.In the mixed radiation field of neutron and gamma，which is generated by ²⁴¹Am-Be，neutron/gamma discrimination performance of the plastic scintillator detector was studied by the linear delay method and the long and short integral time window method，respectively.The neutron/gamma discrimination effect between these two methods was compared via PSD（Pulse Shape Discrimination)diagram and FOM（Figure of Merit).The result shows that the method of charge comparison on neutron/gamma discrimination is better than the method of linear delay.And when it’s of 400 ns long gate and 60 ns short gate in the charge comparison，EJ276 has the best discrimination on neutron/gamma with lowest misjudgment ratio.

Key words: Neutron/gamma discrimination, Pulse shape discrimination, The plastic scintillator detector, The linear delay method, The long and short integral time window method, Figure of merit