Using terahertz wave time-domain spectroscopy system，we measured the terahertz wave time-domain spectroscopy of the corn oil between 0.2 and 1.4 THz. Taking care of the effect of the utensil，we employed a novel iterative algorithm to analyze the optical properties of the corn oil. In contrast to most of the published experiments，the iterative algorithm further improves the accuracy of the parameter extraction, and we are able to reliably investigate the samples. The results show that the novel calculating method provides a guidance for detecting the quality of seed oils.