The invention relates to a method for preparing an oil well cement delayed coagulant and an application method thereof. The preparation method comprises the following steps: dissolving an alkenes monomer having an anion sulfonic acid group, the alkenes monomer having ammonium cations, and an unsaturated monomer containing a carboxylic group in deionized water, adjusting the pH value of a system, adding an initiator under nitrogen introduction condition, and continuously reacting the materials in constant temperature water-bath to obtain the oil well cement delayed coagulant. The application method is characterized in that micro silicon is mixed with glass beads, a fluid loss agent, a dispersant, the obtained oil well cement delayed coagulant and cement according to ratio, and adding water to prepare a cement mortar system. The oil well cement delayed coagulant has the beneficial effects that 1) under high temperature environment, the oil well cement delayed coagulant has the advantages of good stability, good degrading resistance and high temperature resistance; 2) the application temperature difference scope is large which can reach 50-150 DEG C; and 3) an ideal slow-setting effect can be reached in the cement system, super-retarding phenomenon is not generated, intensity development of cement stone at top is fast, and requirement of well cementation with large temperature difference can be satisfied.