Abstract: Oil-water suspension is formed after demulsifier is added into water-content heavy crude oil, and its viscosity can not be accurately measured by conventional coaxial cylinder viscometer.To research the influence of demulsifier on rheology of watercontent heavy crude oil, the torque of oil-water suspension with demulsifier added and different mass fractions under the condition of different temperatures is tested by adopting torque-measurable blender, and its relative viscosity is computed.Research conclusion suggests that demulsifier at low temperature can remarkably decrease the viscosity of water-content heavy crude oil and improve its flow behavior, but demulsifier at high temperature has a scarce influence on the viscosity of water-content heavy crude oil.