To predict the fatigue life of SPAS ECU bracket exposed to random vibration loads, the equivalent load deriving methods were investigated. The dynamic behavior of a system exposed to a random load, such as the approach in the response spectrum analysis, can be expressed as the maximum acceleration response of single degree of freedom systems. When the first eigen-mode is dominant, it is possible to apply a static load to the bracket assuming that the equivalent acceleration is the representative response of the system. The expected fatigue life derived from the static analysis result and the stress-life relation. Modal parameters, strain and acceleration data obtained from the tests are utilized for the verification of the FE model. Also, the appropriate sigma level was derived from comparing the actual failure load with the RMS response of the analytical model. It is expected that the method reviewed in this paper will contribute to the quick decision making in the initial shape design state where local shape change frequently occurs.