Polarity determines the oil resistance property of elastomers. In this work, three bio‐based polyester elastomers (BPEs) with different mass fraction of ester groups (E) are designed and synthesized aiming to study the relationship of E and oil resistance performance, and to obtain bio‐based elastomer materials with tunable oil resistance. Through adjusting the chain length of monomers, E of poly(ethylene glycol/1,3‐propanediol/succinate/adipate/itaconate)(PEPSAI), poly(1,3‐propanediol/1,4‐butanediol/succinate/adipate/itaconate)(PPBSAI), and poly(1,3‐propanediol/1,4‐butanediol/sebacate/adipate/itaconate)(PPBSeAI) are ≈50.39%, 48.55%, and 39.68%, respectively. Results show that E has great influence on the oil resistance of BPEs. After being immersed in IRM‐903# oil for 72 h at room temperature, the changes in mass and volume of BPEs decrease along with the increasing mass fraction of ester groups, indicating improved oil resistance performance. PEPSAI with the highest mass fraction of ester groups presents better oil resistance and lower Tg (better low‐temperature resistance) than one of the most used commercial oil‐resistant rubber nitrile rubber (N230S). Thus, this work provides a promising strategy to obtain bio‐based oil resistant elastomers with practical value.