The invention provides a method and a system for multi-wavelength laser time-sharing ablation of a solar cell dielectric film. The method comprises the steps that at least two coaxial lasers with different wavelengths are adopted, the solar cell dielectric film is sequentially ablated in a time-sharing mode, in one period, each laser emits light one time in turn according to a certain light emitting time interval, and light spots formed by all the lasers in the period are overlapped; the energy density of each laser is higher than the damage threshold value of the corresponding ablation material, and the wavelength of each laser is smaller than the cut-off absorption wavelength of the corresponding ablation material. According to the invention, a multi-wavelength method is adopted, the surface passivation layer of the battery piece is damaged by utilizing the laser with one wavelength, the reflection of the laser to the laser with the next wavelength is reduced, and the ablation capability of the laser with the next wavelength can be better exerted, so that the processing speed is improved, and the efficiency and the productivity are improved under the synergistic effect of the twowavelength lasers.