In order to explore the formation and flow characteristics of natural gas hydrate in oil-gas mixed transportation pipeline, the safe operation law of natural gas hydrate slurry in actual mixed transportation pipeline was obtained. The flow experiment of natural gas hydrate slurry in oil-water emulsion system was carried out by high pressure natural gas hydrate experiment loop. The influence of different initial pressure, initial mass flow rate and dosage on the induction time of natural gas hydrate formation, apparent viscosity and density of slurry in the tube and the volume fraction of hydrate were studied by the control variable method, and the following important research conclusions were obtained: The higher the initial pressure is, the shorter the induction time of hydrate formation is, which is shortened by 51.7% from 1.47 h at the initial pressure of 5.3 MPa to 0.71 h at the initial pressure of 6 MPa. The more intense the hydrate reaction is during the formation process, which is not good for the safety of transportation. The larger the initial mass flow rate is, the longer the induction time of hydrate formation is, which increases by 18.4% from 0.76 h at the initial flow rate of 895.3 kg?h-1 to 0.90 h at the initial flow rate of 1414.6kg?h-1. The smaller the fluctuation range of apparent viscosity is, the more stable and safe the transportation process is. Increasing the dose of polymer inhibitor has little effect on the induction time of hydrate. However, the more stable the hydrate formation stage is, the smaller the volume fraction of hydrate in the pipe after hydrate formation is, and the better the transport of slurry. In the process of flow, if the flow rate decreases, the pressure drop increases, indicating that the aggregation of hydrate volume fraction is obvious and the apparent viscosity of the slurry in the pipe is large, which leads to a greater risk of pipeline blockage.