Welding experiment on flux cored wire E71T-1C for nuclear power engineering were carried out and then the deposited metal were subjected to post-weld heat treatment（PWHT）,which were annealed at 480 ℃、550 ℃、620 ℃、690 ℃、760 ℃ for 16 hours.Optical microscope,material testing machine,impact testing machine and scanning electron microscope were used here. It is shown that,the microstructure is composed of ferrite,fine ferrite and second phase after the specimen is annealed below 690 ℃. When the annealing temperature reaches 760 ℃,the microstructure consists of blocky ferrite and a small amount of pearlite coupled with second phase. As the temperature increase,the precipitates nucleate and grow at grain boundary,in addition,the impact toughness value decreases. When the annealing temperature is raised to 690 ℃,the impact value tested at-20 ℃ is the lowest,that is,95 J. Typical impact fracture morphology and sound impact properties are illustrated by the macrostructure and microstructure of all deposited metal fracture samples.