The present invention relates to a preparation method for 4-(4-aminophenyl) morpholin-3-one. Said method comprises : using p-nitroaniline as a raw material, successively performing an amidation reaction and a catalytic hydrogenation reaction to obtain a p-acyl-substituted aminophenylamin, and then sequentially performing an amidation reaction, a halogenation reaction or a sulfonylation reaction with 1, 4-dioxane-2-one to prepare N-(2-substituted ethyloxyacetyl) p-acyl-substituted aminophenylamin, performing a condensation cyclization reaction under the action of a base to obtain 4-(4-substituted acylaminophenyl) morpholin-3-one, and finally removing an acyl protecting group, so as to obtain a target product. The raw materials used in the present invention are cheap and easy to obtain. The method of the present invention is easy to operate, and has low cost. The reactions involved in each step have high activity and specificity, and are easy to carry out, and the products have high purity and high yield.