Abstract: Introduces the statue of water in oil and measure method of water content rate, and makes a test study on such effective problems as influence of ware content on crude rheological property, on pipeline operation and on equipment in combination with recent actual situation in Mahuining Pipeline. It is pointed out that: (1) the viscosity and pour point of crude oil will be increased with large proportion of water content to a certain extent. When water content rate is less than 5%?there will be few influence on crude rheological property, (2)heavy water content crude will bring unstability to pipeline's operation and increase pipeline energy consumption evidently; (3)Jingma crude has strong corrosiveness to pipeline and equipment due to its water contained, which affects heater's normal operation; (4)Jingma crude of heavy water content 3 m below oil tank level shall be avoided to enter into the pipeline concentrately. This part of the crude should be transported with Maling crude by means of mixing process.