Blade assembly method on a rotor hub of a wind turbine, wherein the wind turbine comprises: - a tower, - a nacelle comprising a generator - a rotor comprising a hub; wherein the nacelle and the rotor are disposed on top of the tower; and - three blades (11, 12, 13) intended to be attached to the hub of the rotor disposed on top of the tower; and wherein the method comprises the following steps: • a first step wherein a first blade connection flange of the hub is located in a first azimuthal position and a first blade is attached in a substantial horizontal position to the first blade connection flange of the hub; • a second step wherein the first blade connection flange of the hub having the first blade attached is rotated in a first direction; • a third step wherein a second blade is attached in a substantial horizontal position to the second blade connection flange of the hub; • a fourth step wherein the hub having the first blade and the second blade respectively attached to the first connection flange and the second connection flange is rotated; and • a fifth step wherein a third blade is attached in a substantial horizontal position to the third blade connection flange of the hub; characterised in that in the second step the rotation of the first blade connection flange of the hub having the first blade attached in the first direction is carried out until the second blade connection flange of the hub is located in the first azimuthal position; in that in the third step the second blade connection flange of the hub is located in the first azimuthal position; in that in the fourth step the rotation of the hub having the first blade and the second blade respectively attached to the first connection flange and the second connection flange is carried out in a second direction opposite to the first direction until a third blade connection flange of the hub is located in a second azimuthal position; and in that in the fifth step the third blade connection flange of the hub is located in the second azimuthal position. - a tower, - a nacelle comprising a generator - a rotor comprising a hub; wherein the nacelle and the rotor are disposed on top of the tower; and - three blades (11, 12, 13) intended to be attached to the hub of the rotor disposed on top of the tower; and - three blades (11, 12, 13) intended to be attached to the hub of the rotor disposed on top of the tower; and wherein the method comprises the following steps: • a first step wherein a first blade connection flange of the hub is located in a first azimuthal position and a first blade is attached in a substantial horizontal position to the first blade connection flange of the hub; • a second step wherein the first blade connection flange of the hub having the first blade attached is rotated in a first direction; • a third step wherein a second blade is attached in a substantial horizontal position to the second blade connection flange of the hub; • a fourth step wherein the hub having the first blade and the second blade respectively attached to the first connection flange and the second connection flange is rotated; and • a fifth step wherein a third blade is attached in a substantial horizontal position to the third blade connection flange of the hub; • a first step wherein a first blade connection flange of the hub is located in a first azimuthal position and a first blade is attached in a substantial horizontal position to the first blade connection flange of the hub; • a second step wherein the first blade connection flange of the hub having the first blade attached is rotated in a first direction; • a third step wherein a second blade is attached in a substantial horizontal position to the second blade connection flange of the hub; • a fourth step wherein the hub having the first blade and the second blade respectively attached to the first connection flange and the second connection flange is rotated; and • a fifth step wherein a third blade is attached in a substantial horizontal position to the third blade connection flange of the hub; characterised in that in the second step the rotation of the first blade connection flange of the hub having the first blade attached in the first direction is carried out until the second blade connection flange of the hub is located in the first azimuthal position; in that in the third step the second blade connection flange of the hub is located in the first azimuthal position; in that in the fourth step the rotation of the hub having the first blade and the second blade respectively attached to the first connection flange and the second connection flange is carried out in a second direction opposite to the first direction until a third blade connection flange of the hub is located in a second azimuthal position; and in that in the fifth step the third blade connection flange of the hub is located in the second azimuthal position.