The thermal fatigue behavior and mechanical fatigue behavior of board level solder joint were investigated by experimental testing and numerical simulation. And two kinds of solder materials, including traditional eutectic lead-tin solder and SAC305 lead-free solder, were considered. Results show that the lead-free solder (SAC305) joint has a longer thermal fatigue lifetime, but a shorter mechanical fatigue lifetime than the eutectic solder joint. Therefore, the evolutions of inelastic strains, including creep and plastic strain, caused by thermal fatigue and mechanical fatigue loading in the solder joint were analyzed by a finite element method. And the difference of solder joint’s thermal fatigue and mechanical fatigue behavior was presented