A prolonged time heat resistance test has been made on modified(KNS-102), hydrogenated(KNS-106) bisphenol-A type and novolac(KNS-611) type epoxy resin based neutron shielding materials. Test conditions are as follows : temperature : 130℃, heating period : 30, 50, 70 and 100 days, ambient gas : air. The high temperature conditions did not result in a measurable loss of the onset temperature of neutron shielding materials. The degradation constant of above-mentioned neutron shielding materials is calculated to be 0.06089, 0.06588, 0.00838, respectively. In general the prolonged heat resistance of shielding material of KNS-611 has been affected less than those of KNS-102 and KNS-106 by high temperature conditions.