The invention discloses an amphiprotic polycarboxylic acid dispersant for oil well cement as well as a preparation method and an application. The preparation method of the amphiprotic polycarboxylic acid dispersant for oil well cement comprises steps as follows: (1) unsaturated polyether macromonomers are dissolved in distilled water and stirred, an oxidizing agent is added, the mixture is continuously stirred, and a mixed solution is obtained; (2) carboxylic acid monomers and cationic monomers are weighed, distilled water is added, the mixture is stirred uniformly, and a solution A is obtained, a reducer is weighed and dissolved in distilled water, the mixture is stirred uniformly, and a solution B is obtained; (3) the solution A and the solution B are dropwise added to the mixed solution, the mixture is kept at the temperature of 60-70 DEG C for 2-4 h, pH is adjusted, and the amphiprotic polycarboxylic acid dispersant for oil well cement is obtained. The preparation process is simple, water is taken as a solvent, and the production process is green and environmentally friendly. The amphiprotic polycarboxylic acid dispersant for oil well cement can effectively improve the flowability of oil well cement slurry and reduce the viscosity of the cement slurry, has good dispersion and rheological property for the cement slurry, is low in delayed coagulation property and promotes early strength development of set cement.