The present invention relates to a conjugate salt of N,N-dimethylglycine with metal and organic acid, and a preparation method and use thereof. The conjugate salt of N,N-dimethylglycine with metal and organic acid has a following structural formula: [(CH3)2NCH2COO]nM.[Organic acid], wherein, n is 1 or 2; M is selected from an alkali metal ion or a divalent metal ion; the organic acid is selected from an organic polyacid, a C2-C18 linear fatty acid or an aromatic acid. The conjugate salt of N,N-dimethylglycine with metal and organic acid is a conjugate acid salt formed by introducing another organic acid with a hydrophobic group into the salt of N,N-dimethylglycine and a metal ion, so as to modify the hygroscopicity of N,N-dimethylglycine by decreasing the affinity of the salt toward water molecules in the air, or decreasing the affinity or attraction of molecular aggregates formed through crystalline behavior of the salt toward water molecules in the air.