The invention provides a catalyst for producing crotonaldehyde, which takes a complex consisting of alkaline earth metal oxide and a molecular sieve or alumina as a carrier, and is prepared by supporting alkaline metal oxide by adopting an impregnation method. Alkaline earth metal is magnesium, calcium or barium, the molecular sieve is an HZSM-5, Hbeta, HY, USY or rare earth Y(ReY) molecular sieve, the alumina is gamma-Al2O3, and alkaline metal is lithium, sodium, potassium or cesium. The mass ratio of the alkaline earth metal oxide and the molecular sieve or the alumina which are taken as the carrier of the catalyst is 1: 20-20: 1, and the mass of the alkaline metal oxide is 1 to 30 percent of the total mass of the complex consisting of the alkaline earth metal oxide and the molecular sieve or the alumina. Compared with a solid catalyst reported by literature, the catalyst has better low-temperature activity, namely the reaction temperature is lower than that of the catalyst reported by literature when the conversion rate of acetaldehyde is equivalent to the selectivity of the crotonaldehyde. The method also additionally produces tolyl aldehyde with higher added value when synthesizing a main product, namely the crotonaldehyde, and further promotes the economic benefit of the catalyst.