The invention discloses a polyaspartic ester polyurea elastomer and a preparation method thereof. Polyaspartic ester is synthesized by modifying specific primary amine of a component B into secondaryamine with specific maleic acid ester. The gelling time is prolonged, the reaction speed is also reduced, and a polyaspartic ester polyurea coating with good apparent property, high mechanical strength and good weather fastness is obtained. The polyaspartic ester polyurea coating has controllable reaction speed, good weather fastness, good mechanical performance and the like, facilitates construction and substrate wetting, can meet the requirements of flowability and levelling property required by preparation of defect-free coating films and has broad application prospects in the field of metal surface protection, floor pavement, bridge and tunnel corrosion prevention and the like.