Abstract: Raw materials constituting a protective colloid includes: UV epoxy-modified acrylate polymer, heat-expandable particles, plasticizer, active monomer and cationic photoinitiator. A weight percent of the UV epoxy-modified acrylate polymer is 40-65%; a weight percentage of the heat-expandable particles is 2-10%; a weight percentage of the plasticizer is 10-15%; a weight percentage of the active monomer is 10-30%; and a weight percent of the cationic photoinitiator is 1-3%. Besides, a method for using the protective colloid is also disclosed.