The invention discloses a preparation method for a cobalt-containing aqueous solution. Deionized water is used as a solvent, and 0.01 mol/L-0.2 mol/L of cobalt oxalate salt, 0.02 mol/L-2.5 mol/L of ammonium nitrate salt, 0.02 mol/L-2.5 mol/L of potassium nitrite, 0.02 mol/L-2.0 mol/L of formic acid and 0.2 mol/L-1.0 mol/L of a water soluble oxidizing agent are evenly mixed for preparing the cobalt-containing aqueous solution; then ultraviolet rays are adopted for irradiating for 30 minutes; and lasers with the strength being 5 W are used for irradiating for 5 minutes. According to the preparation method, the construction cost is low, the performance is excellent, the electromagnetic pulse resistant effect is good, the preparing technology is simple, design is novel, practicability is high,stability is good, reliability is high, and the preparation method is convenient to use and easy to apply and popularize.