To obtain various data for the accident condition and the optimization of advanced nuclear fuel cladding material, the effects of the heat treatment on mechanical properties and microstructures of Zircaloy-4 material have been studied. Due to phase difference, hardness and tensile strength values increased with annealing temperatures(α, α+β and β region) for 15 minutes before water quenching. The microstructural development with cooling rate after β-annealing was as follows: coarse plate-like ⇒ fine parallel plate ⇒ basketweave ⇒ martensite+Widmanstatten ⇒ martensite. Hardness and yield stress of the alloy increased with increasing cooling rate and reached to 245 VHN and 64 kg/㎟, respectively, for the highest cooling rate. Hardness and tensile strength values increased dramatically at cooling rate above 1600℃/sec. Upon tempering at different temperatures for 1 hour, recrystallization was completed at 700℃ in as-ice brine quenched and as-water quenched specimens, while as-air cooled specimens did not recrystallize up to 850℃. During aging at 760℃, hardness and tensile strength values in as-ice brine quenched and as-water quenched specimens indicated that initial decrease appeared to be due to matrix recovery, polygonization and recrystallization, while the values in as-air cooled specimens did not. The decrease in hardness and tensile strength values occurred during short-time annealing(20 minutes for as-ice brine quenched and 40 minutes for as-water quenched) at 760℃. Possibly due to precipitation hardening, these values increased to a maximum (207 VHN for as-ice brine quenched and 203 VHN for as-water quenched) at longer aging times. Further aging decreased the strength values because of precipitate coarsening and grain growth.