The construction of a reactor cold neutron source(CNS) will be completed in the near future.To evaluate performance of the CNS

a neutronics calculation using MCNP4C code has been carried out.The results show that the average neutron flux in the moderator is 6.69×1013/cm2.s

and the cold neutron gain factors corresponding to 4- and 6- wavelengths are 16 and 32

respectively.The results also indicate that different ratios of ortho-H2/para-H2 have an obvious impact on cold neutron spectrum in the moderator

but within 3 K of the moderator temperature changes

the spectrum varies slightly.