Abstract: The present invention discloses a special modified expandable polystyrene copolymer particle for a lost foam, which respectively comprises the following parts by weight: 90 to 100 parts of styrene; 3 to 8 parts of methyl methacrylate; 100 to 140 parts of deionized water; 0.2 to 0.5 part of benzoyl peroxide; 0.2 to 0.5 part of dicumyl peroxide: 0.1 to 0.5 part of tert-butyl peroxybenzoate: 0.001 to 0.01 part of anionic surfactant; 1 to 2 parts of suspension concentrate; 5.0 to 10.0 parts of foaming agent; 0.1 to 0.4 part of nucleator; 0.2 to 2 parts of organic bromine; 0.01 to 0.1 part of molecular weight regulator having the effect of increasing molecular weight, and 0.3 to 0.5 part of surface coating agent.