The fuel tank should keep the fuel stably at any vehicle driving condition but sometimes, the fuel tank can’t store fuel stably due to crack because the vehicle is driven at the various environmental conditions . In case of extreme hot ambient driving condition, the fuel tank pressure is increased because of fuel boiling. In case of normal ambient temperature, before fuel boiling and large engine purge condition. The fuel tank pressure is decreased. The repetitive excessive fuel tank pressure change will lead to damage the fuel tank. The fuel tank crack can lead to fuel leakage from the fuel tank that can lead to damage the vehicle such as fire. Until now, the analysis results of the fuel tank crack is the negative pressure due to engine purge and the decreased canister venting performance because of the dust, so canister venting performance have be improved but the fuel tank crack have not been solved. So the purpose of this study is to research the root cause of fuel tank crack from a fatigue point. The various evaluations will be executed to check the maximum and minimum fuel tank pressure considering fuel boiling characteristic, evaporative canister venting performance, fuel tank venting valve performance, engine purge pressure and the each extreme environmental conditions, and then the CAE simulation will be executed using each fuel tank pressures to check the concentrated stress point and the fuel tank durability performance, and then the fuel tank component test will be executed to check the strain at the fuel tank weak point from CAE simulation and the fuel tank durability test will be executed.