Disclosed are a compound of the following formula (I) or a pharmaceutically acceptable salt thereof, a preparation method thereof, pharmaceutical compositions and uses thereof in the preparation of a medicine for inhibiting HIF prolyl hydroxylase or a medicine for promoting the generation of endogenous EPO, wherein in the formula (I), R1 and R2 are each independently hydrogen R3 is hydrogen or C1-3 alkyl and Ar is an aromatic ring or an heteroaromatic ring selected from a naphthalene ring, a pyridine ring, a thiophene ring, a furan ring and a substituted benzene ring.
