In order to investigate performance characteristics of deteriorated subway rolling stocks, several engineering assessment methods, such as the acceleration, vibration, and braking performance tests, were carried out on subway electric multiple units (EMUs) with over 20 years operation. According to the testing results, in vibration and braking performance of EMUs, the similar performance results were obtained as compared with newly manufactured EMUs. However, in terms of acceleration performance characteristic, below reference value (3.0 km/h/s) has been obtained. This is mainly due to performance deterioration of EMUs including traction motor. In this investigation, the results on precision diagnosis evaluation of deteriorated EMUs were provided through the overall evaluation of corrosion testing and structural performance of car body in subway EMUs.