Abstract: A new complex type of rapeseed oil fatliquoring agent with excellent performance was synthesized by the reactions of ester exchange，ethoxylation and hydroxylation. Infrared spectroscopy (IR) was used to characterize the structure of the products. A preferred synthesis process was given as follows：The ester exchanged oil was first modified by hydrogen peroxide at 50 ℃ for 6 h，when acetic acid was chosen as active oxygen carrier，strong-acid ion exchange resin was chosen as catalyst，and their dosage was 40% and 5% of the ester exchanged oil in weight respectively. Then the epoxidized oil was modified by polyethylene glycol (PEG) at 55 ℃ for 4 h，when the ratio of epoxidized oil and PEG in weight was 1.67∶1，the dosage of KOH was 1% of the epoxidized oil in weight. The product was used as fatliquoring agent of leather. The leather fatliquored with this product showed good fullness，softness，water-resistance，elasticity and silky feeling.