The invention discloses a preparation method of a durability-enhanced alkali-free liquid accelerator. According to the preparation method, maleic anhydride and urea are acylated to prepare an acylatedproduct, then the acylated product is subjected to copolymerization with acrylamide and acrylic acid to prepare a suspension stabilizer, and the suspension stabilizer is used for the preparation of the alkali-free liquid accelerator. By introducing the suspension stabilizer with an amide structure, which is prepared through the acylation of the maleic anhydride and the urea, the cohesiveness of the liquid accelerator is improved, the generation of precipitation is effectively inhibited, the stability of mother liquor storage is greatly improved, and the stability can reach 15 months or more than 15 months; and the amide structure and the urea can promote the development of early strength, so that the early strength of concrete can be improved.