Abstract: Using a self-designed experiment system for water mixed transport of heavy oil and taking the simulated heavy oil prepared from liquid paraffin and solid paraffin products as a research object, the experiment for water mixed transport of heavy oil is carried out under low-temperature conditions in winter. Two flow patterns such as ideal aqueous suspension dispersed flow and finite plug suspension dispersed flow are observed. Based on the hypothesis of two flow patterns consistent with laminar flow theory, the relationship of apparent viscosity of oil and water mixture with flow pattern, water content and pipe diameter are analyzed using Darcy's law. The results show that when the water content is higher than 80% and temperature of oil and water mixture is far lower than condensation point of heavy oil, the oil and water mixture in the pipeline will appear steady ideal aqueous suspension flow pattern, when the water content is below a certain level, flow pattern of oil and water mixture shifts from the ideal aqueous suspension flow pattern to the finite plug aqueous suspension flow pattern, but plug length and spacing are relatively stable and good fluidity are also shown, and internal diameter of the pipeline will affect formation of plugs in the water mixed transport. When the internal diameter is smaller, it will be more prone to plug.