Abstract: This paper studies a globally adaptive and practical output-tracking control of linearly parameterized nonlinear systems with uncontrollable unstable linearization. These class systems are neither linearizable in the feedback nor affine in the control input. The asymptotic output tracking (even local) is usually not possible because the linearized system has uncontrollable modes whose eigenvalues are on the right half plane. Using the modified adaptively adding a power integrator technique as a basic tool, we construct a smooth adaptive state feedback controller that can ensure all signals of closed-loop systems are globally, uniformly and ultimately bounded and steer the output tracking error to a small neighborhood of the origin. Simulation results show that the controller is feasible and effective.