A sewage discharge experiment was carried out using an annular flume to study the characteristics of the mixing and transportation of sewage water in estuarine and coastal areas. The effects of sewage ejection direction, sewage discharge height, and temperature on the characteristics of transportation and dispersion of sewage in environmental water were investigated, providing references for this study. The experimental results show that the dilution and dispersion of sewage in environmental water are mainly affected by the horizontal and vertical angles. With a smaller the angle between the environmental water flow direction and the sewage water discharge direction, the distance required for homogeneous dispersion of sewage in the water will be longer. High-temperature sewage requires a longer distance for thorough dilution and dispersion than normal-temperature sewage. Due to the limited depth of water in the experiment, the height of sewage discharge had no significant effect on the dilution and dispersion of sewage, and no sewage dispersed to heights above 7. 5 cm in the near field of discharge.