A type of MoS2 nanoparticle with a spherical-like shape is chemically synthesized with favorable third-order and suppressed second-order nonlinear optical response, which results from the isotropy induced by the geometrical uniformity of nanoparticles and an artificial symmetry center. It is found that the linewidth of third harmonic signal is broadened due to the self-phase modulation effect, another third-order nonlinearity. Moreover, the intensity of harmonic signal can be conveniently adjusted by controlling the polarization state of applied optical field. The artificially designed material morphology may provide a reference for designing all-optical modulation devices.