The present invention discloses a waterborne dimer acid amide curing agent, a preparation method and the application thereof, the waterborne dimer acid amide curing agent can be well dispersed in the water for dissolution, the concentration of the solid is 30 to 40 percent, the amine value is higher, which can achieve more than 200mgKOH/g, furthermore, the toxicity is low, and the present invention has no pollution to the environment; at the same time, the raw materials are easy to be obtained, and the cost is low. The preparation method adopts the industrial level dimer acid and piperazine derivatives for low-temperature salification and high-temperature condensation, so as to form the polyamide curing agent, the curing agent can generate the water emulsion with the solid content of 30 to 40 percent by emulsifying under certain temperature, and then the waterborne coating can be prepared by the combination of the water emulsion and the epoxy resin water emulsion with the solid content of 50 percent.