Abstract: When transporting waxy crude oil in pipeline at ambient temperature, depressant is added to reduce pour point and improve low temperature flowability. There are two kinds of depressant of polymeric compound; homopolymer and copolymer. Several polymer depressants that are commonly used in resent years at home and abroad are introduced respectively, concerning its synthesis, chemical structural formula and applications. Unitary depressant is hard to reduce effectively the pour point and viscosity of crude oil because crude oil is made up of multiple compounds. Therefore, it is suggested that the relationship between different depressants and crude oil with specific components be analysed, and depressants of various kinds recompounded to form a multicomponent depressant, so as to deal with waxy, viscous crude oil in pipeline.