The reorientation of 2D materials caused by nonlocal electron coherence is the formation mechanism of 2D material spatial self-phase modulation under laser irradiation, which is widely known as the “wind-chime” model. Here, we present a method that provides strong evidence for the reorientation of 2D-material-induced spatial self-phase modulation. The traditional “wind-chime” model was modified by taking into account the attenuation, i.e., damping of the incident light beam in the direction of the optical path. Accordingly, we can extract the nonlinear refractive index of a single ${\mathrm{MoS}}_2$ nanosheet, instead of simply obtaining the index from an equivalent ${\mathrm{MoS}}_2$ film that was constructed by all nanosheets. Our approach introduces a universal and accurate method to extract intrinsic nonlinear optical parameters from 2D material systems.