Abstract: Oil sample taken from oilfield or pipeline has a high water cut, so, dehydration is of necessity when the test is carried out on a physical and rheological behavior of oil sample in laboratory. The research showed that the most cost-effective dehydration method is the electric dehydration method, therefore, on the principle of getting a better dewatering result without altering oil characteristics, heating temperatures and dewatering intervals should be applied separately to different oil samples based on the oil characteristics when adopting this method, at the same time, the dehydrator's cover should be designed with a hemicycle with groove so as to make the water droplet condensed on the cover flow into the groove instead of the oil, and the volume of oil sample to be tested should be 3/4 of the internal volume of dehydrator. The physical and rheological behavior of the dewatered oil sample can be determined only after it has to be placed for 48 hours at room temperature in order to reflect ite true behavior.