Abstract: The present disclosure discloses a median line method in maritime delimitation based on an earth ellipsoid. The method is implemented by calculating a coordinate point of a median line of a maritime space, including: determining two delimitation base points A and B on a coastline of a certain country and a delimitation base point C on a coastline of the other country; calculating to obtain an equidistant point O with the same geodetic distance from the two points A and B; solving the geodetic distance from the point O to the point C according to the geodetic coordinates of the equidistant point O; determining whether the difference between respective geodetic distances of OC and OA is less than a first target error; if the difference is less than the first target error, then taking O as a point on a solved median line; and otherwise, adjusting the geodetic distance, and recalculating the coordinates of the point O.