The invention discloses a rapid and accurate positioning method of an overwater gravity anchor. The rapid and accurate positioning method comprises the following steps: setting two positioning points on a crane positioning ship; establishing a reference equation through a relationship of trigonometric functions; and after measuring coordinates of the two positioning points, indirectly obtaining coordinates of a gravity anchor through the reference equation. The rapid and accurate positioning method provided by the invention is free from influence of external environments, can be subjected to all-weather operation, needs no stable platform erecting instrument, is accurate in measurement, convenient and efficient, greatly shortens measurement positioning time, and has relatively great promotion value.