The invention discloses a waterborne polyurethane elastomer. The waterborne polyurethane elastomer comprises, by weight, 20 parts of ethylene glycol, 10 parts of tripropylene glycol, 5 parts of 2-n-amylpropane-1,3-diol, 30 parts of isocyanate, 2 parts of 1,1-dimethyl-silanol 1-acetate, 5 parts of methyl isocyanate, 5 parts of propylene isocyanate, 3 parts of methyl 2,3-diethyl-1-( trimethyl silicyl)-2-cyclopropene-1-carboxylic ester, 30 parts of acrylate, 5 parts of modified molecular sieve, 5 parts of hydrophilic chain extender, 5 parts of enhancer, 2 parts of defoaming agent and 2 parts of leveling agent. By the arrangement, the mechanical performance of the whole waterborne polyurethane elastomer can be kept in a good state under a large day and night temperature difference.