To ensure the testing data accurate and reliable of salt-spray test equipment, measurement model of salt-spray sedimentation ratio uncertainty evaluation was established and used to analyze uncertainty sources combining with real experiment system, based on which, sedimentation rate uncertainty of salt-spray for locomotive vehicles electronic devices was assessed, and the results met requirements of standard. This method ensured the correctness and repeatability of shell quality test of locomotive vehicles electronic devices, and provided guidance for equipments structure improvement.