The invention relates to the field of surfactants, in particular to a double-alkyl salt-free imidazoline surfactant, a preparation method thereof and application of the double-alkyl salt-free imidazoline surfactant as a low-foam surfactant. A batch feeding method is adopted to synthesize the double-alkyl salt-free imidazoline surfactant. The surfactant has the advantages of less side products, high purity, environmental friendliness, low foam and superior corrosion inhibition performance, can meet a plurality of functional demands in the industries of power station boiler cleaning, steel plate cleaning, precise instrument cleaning and the like, and has important scientific research and economic values.