The present invention provides an aqueous emulsion having excellent polymerization stability and standing stability and a redispersible powder. Specifically, the present invention relates to an aqueous emulsion of a polymer obtained by polymerizing an acrylic monomer in the presence of a polyvinyl alcohol containing an acetoacetic ester group; wherein the polyvinyl alcohol containing an acetoacetic ester group has block character [.eta.] of 0.3 to 0.6, hydrolysis degree of at least 97% by mol and acetoacetic esterification degree of 0.01 to 1.5% by mol, and the value obtained by dividing the maximum value by the minimum value of the respective average acetoacetic esterification degree for each of the polyvinyl alcohol containing an acetoacetic ester group separated by particle size of 44 to 74, 74 to 105, 105 to 177, 177 to 297, 297 to 500 and 500 to 1680 .mu.m is 1.0 to 3.0. Also, the present invention relates to a redispersible fiber obtained by drying the aqueous emulsion.