In the process of automobile industrialization, integrated electric drive systems turn to be the mainstream transmission system of electric vehicles gradually. The main sources of noise and vibration in the chassis are from the gear reducer and motor system, as a replacement of engine. For improving the electric vehicles NVH performance, effective identification and quantitative analysis of the main noise sources are a significant basis. Based on the rotating hub test platform in the semi-anechoic chamber, in this experiment, an electric vehicle equipped with a three-in-one electric drive system is taken as the research object. As well the noise and vibration signals in the interior vehicle and the near field of the electric drive system are collected under the operating conditions of uniform speed, acceleration speed, and coasting with gears under different loads, and the test results are processed and analyzed by using the spectral analysis and order analysis theories. Combining the traditional analysis method above, an evaluation process method focusing on the order contribution ratio is proposed, which is employed to quantitatively analyze the main noise sources and guide the focus of noise reduction. The results indicated that the main order contribution sources of noise are the 21st and 42nd orders from the first-stage gear, and the 48th order from the motor. In addition, it is also relatively prominent that the switching frequency component of the inverter in the signal within low-rotational speed. In the speed range of 1000-9600 rpm, the peak value of vibration energy and its change tendency caused by load can be effectively reflected by high contribution proportion of specific orders. It is concluded that the proposed method is equipped to extracting the key sources of vibration problems under various working conditions.