Abstract: The online mixed transportation of high-viscosity oil in the Rizhao-Dongming crude oil pipeline is realized by the static mixer, and a great amount of production data and experience is accumulated. In this paper, the effects of the mixed transportation technology adopted in the Rizhao-Dongming crude oil pipeline, the properties of transported oil and the movement of batching interface on the operating parameters, and the effects of oil setting on the transportation startup were introduced. Then, the events of viscosity anomaly were taken as the example to comparatively analyze the important parameters and data before and after the events, e.g. pipeline flow rate, pressure, viscosity and hydraulic slope. And it was ultimately determined that the high mixing ratio of heavy oil and the clump of impurity particles deposited in partial pipelines are two key influential factors. In order to ensure the safe operation of pipeline and avoid the reoccurrence of viscosity anomaly event, it is suggested to strictly control the operation parameters (e.g. mixing proportion and viscosity) and define the pigging frequency based on the sampling data, combined with the actual production situations, so as to optimize pipeline production and operation. The research results provide the technical support for safe transportation of mixed oil.