Drag reducer is the key additive of fracturing fluid for unconventional reservoir reconstruction，such as tight sandstone and shale，and its performance will directly influence on the fracturing operation effect. Polymer drag reducer，surfactant drag reducer and multi-component drag reducer were introduced，and the advantages，disadvantages and research progress of the three drag reducers were analyzed. The turbulent drag reduction and drag reduction failure mechanism of drag reducer were emphatically described. The research progress of nanomaterial in fracturing drag reduction was summarized. This paper pointed out that in unconventional reservoir fracturing environment such as high temperature，high shear and complex medium，the new type of multi-functional composite drag reducer with the advantages of stability，high efficient drag reduction，low reservoir damage， strong sand carrying capacity，easy flowback and easy recycling would be an important research direction in future.