Abstract: This paper studied the rheological variations of Daqing crude oil treated with PPD (Pour Point Depressant), and determined the optimal technological parameters as well as compared the experimental results of rapidly cooled treatment and slowly cooled treatment based on plenty of experimental data. The experimental results have showed that the rheological properties of Daqing crude oil treated with DQ₆ PPD have been obviously improved, and its optimal treated temperature is 60 ℃. The experimental results of rapidly cooled treatment is also better than that of slowly cooled treatment.