Abstract: The process of the temperature drop of oil is studied with the temperature measurement system installed in No. 2 breathing roof tank in Qinhuangdao Pump Station. This paper brings forward some new viewpoints about the temperature drop characteristic of oil based on analyzing test data and phenomenon, that is, (1) Daqing oil has three forms——solid, semisolid and liquid in breathing roof tank; (2) the process of temperature drop includes the stages of speedy temperature drop, increment of curdle oil layer and slow temperature drop and (3) the heat loss of crude oil mainly comes from the curding heat. These viewpoints will be helpful to improve the forecast precision for the tanked oil.