The invention relates to a preparation method of an aldehyde gas phase hydrogenation catalyst. The preparation method comprises the following steps that 1, copper-zinc-aluminum alloy seed crystals with the average pore size of 1-10 nm and the particle size of 50-200 micrometers are prepared; 2, the copper-zinc-aluminum alloy seed crystals and a surfactant are added into an oil-water two-phase solution, then the solution is introduced into a reciprocating type reactor, a salt solution of copper, zinc and aluminum and a precipitant solution are titrated into the two-phase solution in a parallel flow mode through two feed inlets, and precipitating and aging are conducted to obtain a precipitation solution; 3, after the precipitation solution is stratified, a water phase is taken to be filtered, washed, dried and calcined, and then the catalyst is obtained. The catalyst prepared by adopting the method is high in activity, large in specific surface area, small in pore size, concentrated in distribution and capable of improving the selectivity of alcohol and has the higher strength and liquid resistance.