Abstract: The prompt neutron decay parameterαfor 300^# research reactor is experimentally studied by the reactor cross power spectral density（CPSD） measurement system.The reactor core is loaded with the used low enriched uranium with a certain burnup.The measurement system uses PCI-6143 high-speed synchronization DAQ and Labview8.5 program as the measurement hardware and development software, respectively.The continuous current signals of neutron in the reactor are acquired by the gamma compensation ionization chambers which are symmetrically positioned in the reactor core.The cross power spectral density,for the two channel signals,is computed using the application program of data acquirement and data process analysis.Finally,using the non-linear least squares method,the prompt neutron decay parameterαis fitted,i.e.α=（83.5±0.6）s^-1.The result accords to the real operation process,which shows that the measurement of the prompt neutron decay parameter α is successful.