The invention belongs to the technical field of nuclear pollution decontamination, and discloses a waterborne low surface tension high viscosity radioactive aerosol suppressant and a preparation method. Acrylamide is used as a main monomer, acrylic acid and styrene are used as functionally modified monomers, and self-emulsifying micro-emulsion polymerization is carried out to obtain the waterborne low surface tension high viscosity radioactive aerosol suppressant. The suppressant is a water-soluble suppressant, and accords with the characteristic of environmental friendliness. The suppressant has a relatively low surface tension, has good wetting wrapping properties to an aerosol, and at the same time has a relatively high viscosity, a film is formed by solidification after the aerosol is suppressed by the suppressant and falls to the ground, the high-viscosity suppressant is more conducive to solidification and recovery of suppressed dust, no secondary pollution to the environment is caused, and the suppressing efficiency adopting the prepared radioactive aerosol suppressant is 87.93% or more. At the same time, the suppressant has good film-forming properties, and thus an application of the suppressant in a nuclear emergency process is more conducive.