The invention discloses a self-foaming sun block and a preparation method thereof. The self-foaming sun block is prepared from deionized water, glycerinum, butanediol, propylene glycol, methyl parahydroxybenzoats, EDTA-2Na, potassium cetyl phosphate, dicyl polyglycoside, allantoin, xanthan gum, dipotassium glycyrrhizinate, ethylhexyl Methoxycinnamate, C12-15 cholesteryl benzoate, C12-20 alkyl polyglycoside, polydimethylsiloxane, caprylic acid/tricaprin, dicaprylyl carbonate, methylenebis-benzotriazolyl tetramethyl butylphenol, ethylhexyl triazone, diethylaminohydroxybenzoyl hexyl benzoate, a VP/eicosylene copolymer, polyhydroxystearic acid, cyclopentasiloxane, tocopheryl acetate, cyclotetrasiloxane, dimethiconol, propyl p-hydroxybenzoate, aluminum stearate, Novec HFE-7100 and the like. The self-foaming sun block disclosed by the invention is good in sunscreen effect, so that people feel relatively fresh and breathable.