The invention discloses a preparation method of a low-temperature silver paste grid line for a silicon heterojunction solar cell. The method comprises the following steps: (S1) printing the grid line on the silicon heterojunction solar cell with a low-temperature silver paste; (S2) drying the printed grid line; and (S3) irradiating the dried grid line by ultraviolet light, and enabling an organic solvent in the grid line to completely volatilize. The contained organic solvent completely volatilizes by irradiating the grid line with the ultraviolet light, so that pollution to the solar cell caused by the organic solvent in a solar photovoltaic power generation operation process is avoided; the conductivity is reduced; and the power generation efficiency of a solar cell module can be effectively kept.