Abstract: The transport capacity can be increased by adding depressant in waxy crude oil to be delivered. In recent years, the trend in studying the depressant formulas home and abroad is to increase their polar group or surfactant group. The mechanism is that the depressant is surfactant, functioning as dispersing wax crystals, which delays the wax-crystal accumulation in gelled crude system containing wax-crystals, and by which jellification is delayed and condensation point is reduced. The multi-formulas principle is discussed and the basis on selecting depressants is provided. It is pointed out that the depressant is not universal to solve problems, especially for the pipeline transporting the waxy and/or high crude at atmospheric temperature.