A silver activation counter has been constructed by plastic scintillator plates along with silver foils for determination the neutron yield of a 2.48kJ plasma focus device, SBUPF1. This counter was calibrated by source removal method with an Am-Be 5 Ci neutron source which was placed above the anode of plasma focus device. Deuterium gas up to 8mbar pressure was injected to this device, and the neutron yield produced by pulsed D-D fusion of plasma focus device was measured by the counter. the neutron yield of SBUPF1 in 8mbar pressure was obtained 3.71±0.32×10 7 neutrons per shot. This result has relatively agreed with the neutron yield measured by silver activation Geiger counters.