For simulating the effect of alternating temperature， which is caused by the weather variations， on the durability of fine coral concrete， mechanical properties of fine coral aggregate concrete and corrosion behavior of its reinforcement under 20-70 ℃ alternating temperature cycles were studied， and the counterparts at constant 20，70 ℃ also were investigated for comparison. The results show that their density values don't show significant difference when the coral concrete samples experience various temperature conditions. However， the porosity of the fine coral aggregate concrete under 20-70 ℃ alternating temperature conditions is about 6% higher than the ones under the constant temperature solutions. Simultaneously， the open circuit potential （OCP）， corrosion current density （i_corr）， and polarization resistance of the reinforcement/concrete interface （R_ct） of the reinforcement under alternating temperature cycles are much lower than their counterparts at the higher temperature of the thermal cycle， while the aforementioned parameters of samples under the former conditions are close to the ones at the constant lower temperature of the cycle. Consequently， it can be concluded that the alternating temperature obviously degrades the coral concrete layer， while its degradation effects on the reinforcement/concrete interface are dramatically declined by the concrete cover layer.