To improve the machining ability of serial robots,an optimized SSI method is proposed to realize online modal identification.The method employed NExT method,modal confidence factor and modal assurance criterion to improve the modal identification accuracy.Next,the machining vibration data at key points in the path of the machining robot are used to identify the mode frequency and damping ratio.Finally,the experimental results show that the optimized SSI method can restrict estimation accuracy in 7%,and the method of optimized SSI method is more accurate than the traditional SSI method.Therefore,if only the modal frequency and the damping ratio are concentrated,the method can realize the online recognition of modal parameters in the cutting path of the machining robot,which can provide the input parameters for the process planning and optimization.