In order to study the effect of laser shock processing on low cycle fatigue behavior of extruded AZ80- T6 magnesium alloy, laser shock peening (LSP) and warm laser shock peening (WLSP) have been carried out on fatigue specimens using Nd: glass laser as well as tensile- tensile fatigue test. The results show that residual compressive stresses generated by LSP and WLSP at 300 ℃ are -125 MPa and -158 MPa, and their fatigue lifes are improved by 11.42% and 75.74%, respectively. The crack initiation time is delayed obviously by WLSP so that fatigue life of AZ80-T6 alloy is improved. Laser shock induced microstructures of magnesium alloy and low cycle fatigue behavior are analyzed and discussed.