The invention relates to a synthetic method for vitamin A intermediate C14 aldehyde. The synthetic method includes the following steps that 1, cyclocitral is used as a raw material and condensed with a chloro-isocrotyl methyl ether Grignard reagent to prepare a C14 alkenyl ether hydroxyl product; 2, the hydroxy group is hydrolyzed into olefin and alkenyl ether at the same time under acid catalysis to obtain C14 aldehyde. The path of the synthetic method is concise, a beta-ionone intermediate is unnecessary, C14 aldehyde is obtained by directly condensing the cyclocitral, and the yield and the purity of C14 aldehyde are high. The product is obtained in an acid system and prevented from deteriorating in a high-temperature strong base environment; the condensation compound of the chloro-isocrotyl methyl ether Grignard reagent is hydrolyzed into olefin and alkenyl ether to obtain aldehyde through hydrolysis in one step.