Abstract: A robust energy efficient joint beamforming and power allocation algorithm is studied for multiple antennas broadcast downlink communication system. The robust energy efficient optimization problem is first formulated as the maximization of the ratio between the system sum rate and the system power consumption subject to a predefined power constraint. The considered fractional programming optimization problem is then transformed into a parameterized polynomial form optimization problem via using the fractional programming theorem and the relation between the user rate and the minimum mean square errors (MMSE). Final, an effective robust energy efficient optimization algorithm is proposed by exploiting the Lagrangian duality theorem and monotonic optimization theorem. Compared to the classical non-robust energy efficient optimization algorithm, the proposed algorithm can obtain an obvious energy efficiency performance gain.