The invention relates to a fountain solution for offset printing, and particularly to an alcohol-free condensation fountain solution containing colloid silica prepared by magnetic activated water and a preparation method thereof. The fountain solution is prepared by the following raw materials, by weight, 6 to 8 parts of glycerin, 0.5 to 0.8 part of dispersant MF, 2 to 3 parts of polyvinylpyrrolidone, 30 to 40 parts of magnetic activated water, a proper amount of acidic buffer, 2 to 3 parts of sodium alginate, 1 to 3 parts of sodium chloride, 2 to 3 parts of colloid silica, 3 to 4 parts of dipotassium hydrogen phosphate, and 1 to 2 parts of fatty alcohol polyoxyethylene ether. The magnetic micromolecule water is used as a solution of the fountain solution, the fountain solution can quickly spread to form a film, the dispersed colloid silica can further speed up adsorption and spread of a hydrophilic film on a printing surface, the wetting effect is improved, and the printing surface can be protected. The fountain solution does not contain volatile alcohols or other harmful substances, is more environmental friendly and safe. The fountain solution can make water and ink balance quickly, no ink accumulates, the printing quality and the printing speed can raised, the condensation fountain solution also is easy to store, hardly go bad, and the condensation fountain solution can be diluted into needed concentration when used.