Provided is an autonomous underwater antenna reclining mechanism. The autonomous underwater antenna reclining mechanism comprises a base, the base is provided with a cylinder arranged in a horizontal manner, a cylinder body of the cylinder is hinged to the base, a piston rod of the cylinder is hinged to a clamp seat, two sides of one end of the clamp seat, close to the cylinder, are each provided with a connection clamping plate, the two connection clamping plates are hinged to two sides of a support, the support is fixedly arranged on the base, the other end of the clamp seat is fixedly connected with an antenna, the hinge centers of the two connection clamping plates and the support are positioned at two sides of the hinge center of the piston rod and the clamp seat, the hinge centers of the two connection clamping plates and the support are higher than the hinge center of the piston rod and the clamp seat, a connecting line of the hinge center of the cylinder body of the cylinder and the base, the hinge center of the piston rod and the clamp seat, and the hinge center of any connection clamping plate of the two connection clamping plates and the support forms a right angled triangle, and the right angle of the right angled triangle is positioned at the hinge centers of the connection clamping plates and the support. According to the autonomous underwater antenna reclining mechanism, automatic switching of vertical and horizontal states of the antenna can be realized.