Harmonic resonance is composed of series and parallel harmonic resonance. It is closely related to the singularity of a network loop impedance matrix or node admittance matrix. It was found that such resonance phenomenon is associated with the singularity of the network matrix. The smallest eigenvalue of the matrix defines the mode of series harmonic resonance. This paper applies this eigenvalue theory and modal sensitivity analysis method to determine which network components contribute significantly to a series harmonic resonance phenomenon. Case study results further confirm the theoretical correctness and effectiveness. Thus, this practical method not only provides significant measures for series harmonic resonance manage, but also support theoretical and experimental bases for the component parameter design.