Real-time monitoring of the rotor vibration signal is a key to ensure rotating machinery running steadily. The coupling source error of rotor roundness error and eddy current displacement sensor error is rarely considered in previous research and vibration monitoring, which causes distortion of the rotor vibration signal, and even causes misjudgment. Taking an actual rotor as an example, a measurement expression of the roundness error is proposed. The errors of two common eddy current displacement sensors are measured and analyzed. The expression of source error which is coupled by roundness error and eddy current displacement sensor error is constructed by Fourier fitting. The mapping relationship between coupling source error and rotor vibration signal is established. Three rotor vibration signal recognition methods are proposed, including the point-point method, the average value method and the max value method. All three methods can effectively recognize the rotor vibration signal. The point-point method is the most accurate, and its recognize error accounts for about 20% . The average value method is simple to calculate, and its recognize error accounts for about 10% . The maximum value method is conservative. However, it helps to effectively avoid misjudgment and its recognize error accounts for about 32% .