Abstract: Ottelia acuminata was a dominant macrophyte in Dianchi Lake prior up through the 1970s, when it was thought to have gone extinct in 1976. Various theories have been proposed as to its extinction, with a particular focus on pollution-driven factors. By comparing the historical records on pollution and fish yields of Dianchi Lake from the 1950s to early 2000, we found that the extinction of O. acuminata from Dianchi Lake occurred earlier than the documented spread of pollution. The surveyed data also demonstrate that the extinction of O. acuminata was likely caused primarily by the massive introduction of grass carp, from1958 to 1973. Future reclamation of lake bays and pollution may yield some impact on the restoration of the O. acuminata population even after the decline of grass carp population.