Several complex esters were synthesized from phthalic anhydride, neopentyl glycol and rapeseed acid. Their rheological properties, biodegradability and tribological properties were measured. It was found that the complex esters have a wide viscosity range of 126~325mm2/s at 40°C with viscosity indices about 127~143, and solidifying points lower than-38°C. The maximum non seizure load of a complex ester with degree of polymerization 1.42 is as high as 735 N, with a wear scar diameter of 0.41mm, superior to mineral oil. The biodegradation rates are higher than 73%, and the thermal stability is good. So these complex esters are a class of green synthetic ester oils with excellent properties.