The invention relates to an acetylene dimerization water-phase catalyst and application thereof. The acetylene dimerization water-phase catalyst is prepared from: a main catalyst, a co-solvent, a solvent and a ligand, wherein the main catalyst is cuprous chloride; the co-solvent is ammonium chloride; the ligand is a sulfonic acid or phosphonic acid ligand. The invention further discloses the application of the catalyst to acetylene dimerization reaction. The invention provides the acetylene dimerization water-phase catalyst and the application thereof; one sulfonic acid or phosphonic acid ligand is added into the catalyst, so that on one hand, the ligand can form a coordination bond with Cu and the reaction activity of Cu<+> can be improved in water; on the other hand, part of Cu<2+> is reduced through the ligand, a condition that a catalytic active component Cu<+> in a reaction solution is converted into the Cu<2+> is inhibited, the content of the Cu<+> is increased and the reaction activity is improved, so that the single-pass conversion of acetylene is increased.