With rising of the running speed of the train, the variation of pantograph–catenary contact force (PCCF) signal increases and the current collection quality between pantograph and catenary becomes worse. In order to explore the ways to optimize the PCCF signal, localization analysis of the value and the change of PCCF signal at the dropper-point are carried out using the method of simulation research in this paper. First, the continuous wavelet transform is adopted, and the variation of the PCCF signal of each dropper-point at the critical frequency is analyzed based on the time–frequency characteristics. It is obtained that the PCCF signal at the dropper-point is characterized by the amplitudes of the wavelength of dropper-spacing and span, in which the contribution degrees are different. Second, the methods of wavelet ridge and the Lipschitz exponents are adopted to analyze the change rate of PCCF signal based on the singularity. It is obtained that the declining rate of PCCF signal on the right side at the dropper-point is greater than the rising rate on the left side when the pantograph runs from the left of the dropper to the right. Finally, the relationship between the amplitude and the change rate of the PCCF signal and the catenary tension is discussed. The results show that increasing the contact wire tension and decreasing the messenger wire tension can reduce the value and the change rate of the PCCF signal at the dropper-points so that the current collection quality between pantograph and catenary is improved.