Abstract: In order to promote the engineering application of polyvinyl alcohol (PVA) fiber reinforced engineered cementitious composites (PVA-ECC) in thermal environment, mechanical property change of PVA-ECC with high-volume of fly ash after thermal treatment was investigated through dogbone specimen tensile test. The single fiber tensile test, single fiber pullout test and single crack tensile test were conducted to explore the performance improvement mechanism of PVA-ECC. The results indicate that PVA-ECC can keep its characteristic of multiple-cracking after thermal treatment by no more than 200℃. Compared to 20℃, tensile mechanical properties are significantly improved after being treated at 50, 100, 200℃, and the rule is: 100℃> 50℃> 200℃.The fiber strength is not a controlled factor for the change of PVA-ECC tensile properties, and a proper thermal treatment enhances chemical bond and frictional bond between fiber and matrix, and thus increases bridge stress and crack complementary energy, which result in the improvements of tensile properties and friction energy dissipation capacity for PVA-ECC. The mechanism analysis of PVA-ECC performance variation provides a sound theoretical basis for PVA-ECC engineering design.