The invention discloses a method for preparing a vitamin A intermediate 2,4-di-double-bond 15-carbon phosphonate. The prior methods use beta-ionone as a raw material and have long synthetic routes which are often more than three steps. The method n uses the beta-ionone as the raw material to perform condensation reaction with ethylene tetraethyl diphosphonate to obtain the target compound 2,4-di-double-bond 15-carbon diethyl phosphonate. The method uses the beta-ionone as the raw material to generate the target product 2,4-di-double-bond 15-carbon phosphonate only through one-step reaction, and has simple process route and great industrial value.