Abstract: In pressurized water reactor, the H₂O/U ratio and ²³⁵U enrichment are important parameters affecting the distribution of neutron spectrum. The variation of two-group neutron spectra with burnup was analyzed under the different H₂O/U ratios and ²³⁵U enrichments. The moderator temperature coefficient was analyzed by using neutron spectrum. The results show that the core has a minimum moderator temperature coefficient with H₂O/U ratio change at given ²³⁵U enrichment condition, and the increase of ²³⁵U enrichment and burnup may not lead to more negative for moderator temperature coefficient.