Recently, the proportion of electronic components is increasing in the automotive vehicle. To protect electronic devices is extremely important in the car driving and maintenance. The fuse box of vehicle has functions to protect the circuit and device when the devices experience an excess current. Also, it is installed in the engine room of the vehicle and experience complex loads such like vibration from the ground, temperature from circumstance and electronic current. The objective of this study is to predict the fatigue lifetime of fuse box under complex environment such like vibration, electronic and heat load. To verify the simulation model of fuse box, various simulations to describe the physical test conditions were performed. And the results of simulation were compared with the test results. One single simulation model was used for the simulations in the different field problem. The stress results from vibration and electro-heat-mechanical coupled simulation were used to calculate the fatigue lifetime of the fuse box components. Finally, the results from fatigue lifetime simulation of the fuse box under complex environment are presented and compared with test results. It also examined the effect of wire bundles.