The invention discloses a method for preparing methallyl alcohol and aldehyde acetal simultaneously by using Sn-beta catalysts. The method comprises the following steps: dealuminizing an H-beta molecular sieve serving as a parent, and grinding and roasting the H-beta molecular sieve and stannum acetate to obtain the Sn-beta catalyst Sn-beta; obtaining the Sn-beta catalysts Sn-beta-Ar and Sn-beta-Ar-Na by aftertreatment methods of Ar pretreatment and Na exchange so as to reduce stannum species outside a skeleton and the B acid content of the catalysts and further improve the catalytic activity and selectivity; and preparing two important chemical products methallyl alcohol and aldehyde acetal simultaneously at low temperature by using the above Sn-beta catalysts, taking methylacrolein as a substrate and taking ethanol as a solvent and a hydrogen source. The Sn-beta catalysts have high activity, and the methallyl alcohol with the yield being 90 percent and the aldehyde acetal with the yield being 96 percent can be obtained; the catalysts have high stability and is not deactivated after being circulated for many times; the reaction is conducted at low temperature without high temperature and high pressure; and the reaction system is a multiphase reaction system, and the catalysts and the products are separated simply and conveniently.