The invention provides an oxoaliphatic-aromatic polyester and a preparation method thereof. The method comprises the following steps: performing an esterification reaction on 3,6-dioxo-1,8-suberic acid, aromatic diol and a zinc oxalate dihydrate catalyst serving as a rection system at the temperature of 100 to 180 DEG C under the protection of nitrogen gas to obtain an esterified intermediate product; performing a condensation polymerization reaction on the esterified intermediate product at the vacuum degree of 200 to 300Pa and at the temperature of 180 to 250 DEG C for synthesis to obtain the polyester. Compared with a conventional synthetic method, the preparation method has the characteristics of environment-friendly reaction process, high polyester yield, high thermal stability and degradation performance of a polyester material, and the like.