Aluminium sulfate has mild acidity, yet the acidity of aluminium sulfate is not taken advantage of in organic synthesis. Here, we utilized aluminium sulfate for the first time in a multicomponent reaction for the synthesis of polyhydroquinoline. A four-component one-pot synthesis of polyhydroquinoline was carried out by condensing dimedone, aromatic aldehyde, ethyl acetoacetate, and ammonium acetate using a catalytic amount of aluminium sulfate (10%) refluxed in ethanol. The present protocol using aluminium sulfate a mild solid catalyst has several merits, such as low cost, high yield, and shorter reaction time, with no byproducts.