Abstract: On the basis of analyzed A,B,C,D-type water drive curves,two categories of water drive curves areproposed, which can not only be applied to predict recoverable reserves and recovery factor in a waterflooding oilfield,but can delermine piston displacement degree indexes. The study shows that the more close to 1 the degree indexes, themore obvious the piston displacement is; whereas the more close to 0, the less obvious the piston displacement.