This paper describes two novel cartesian control algorithms, in order to balance a humanoid robot on a variable slope surface. Two approaches have been developed, one takes into account the body attitude sensors feedback; and the other one, the body forward kinematics feedback. The first method takes the robot's body attitude sensors measures, that is the robot body configuration in the 3D space, and this is the inverse kinematics algorithm's input, which computes the current joints position in order to balance the robot, standing position on a variable slope. The second method, computes the forward kinematics joint positions to obtain the robot body configuration, which is the input of the inverse kinematics algorithm, for balancing the robot. Both methods are tested in NAO humanoid robot platform, and the results are discussed.